Yves Chilliard Frŗdŗric Glasser Anne Ferlay Laurence Bernard Jacques Rouel Michel Doreau INRA, UR1213 Herbivores, Site de Theix, Saint-GenŠs-Champanelle, France Diet, rumen biohydrogenation and nutritional quality of cow and goat milk fat The potential to modify the milk fatty acid (FA) composition by changing the cow or goat diets is reviewed. Ruminal biohydrogenation (RBH), combined with mammary lipogenic and D-9 desaturation pathways, considerably modifies the profile of dietary FA and thus milk composition. The pasture has major effects by decreasing saturated FA and increasing FA considered as favorable for human health (c9-18:1, 18:3n-3 and c9t11-CLA), compared to winter diets, especially those based on maize silage and concentrates. Plant lipid supplements have effects similar to pasture, especially lin- seed, but they increase to a larger extent, simultaneously several trans isomers of 18:1 and, conjugated or non-conjugated 18:2, especially when added to maize silage or concentrate-rich diets. The goat responds better for milk 18:3n-3 and c9t11-CLA, and sometimes less for c9-18:1, and is less prone to the RBH trans-11 to trans-10 shift, which has been shown to be time dependent in the cow. The respective physiological roles of most milk trans FA have not been studied to date, and more studies in rodents and humans fed dairy products modified by changing ruminant diet are required before recommending a larger use of lipid sources and how to combine them with the different feeding systems used by dairy farmers. Keywords: Diet composition, biohydrogenation intermediates, mammary metabolism, fatty acid desaturation, milk fatty acids. 828 DOI 10.1002/ejlt.200700080 Eur. J. Lipid Sci. Technol. 109 (2007) 828–855 1 Introduction Milk fat secretion and milk fatty acid (FA) composition are of great interest with regard to human nutrition. Apart from their contribution to dairy products’ sensorial quality and to the amount of dietary energy, different lipid and FA compounds (short- and medium-chain saturated, branched, mono- and polyunsaturated, cis and trans, conjugated FA, etc.) present in ruminant milk fat are indeed potentially positive or negative factors for the health of consumers [1–3]. Dairy products provide indeed 25–60% of the overall saturated fat consumption in Europe, which makes them, since decades, a target of dieticians’ criticism due to the negative effects of excessive consumption of saturated FA on human health [4]. The image of saturated FA should, however, be weighed by the fact that C 12 –C 16 saturated FA are thought to be atherogenic only when consumed in excessive amounts, that 18:0 has no atherogenic effect and that saturated fat could even be protective when compared to a low-fat, high-carbohy- drate diet [5, 6]. The allegedly atherogenic effect of certain trans monounsaturated FA (MUFA) [7] has not been con- firmed for vaccenic acid (t11-18:1), the main isomer present in milk [8, 9]. The intake of some trans isomers of 18:2 seems to be particularly harmful, although further research is needed to discriminate between industrial and ruminant isomer profiles [10]. In other respects, it has been shown in humans that the consumption of milk fat [11] could sometimes decrease cardiovascular and/or metabolic syndrome risk factors. Branched-chain FA, such as iso-15:0, anteiso-15:0 and iso-16:0, have been shown to present anti-cancer activity in human breast cancer cell models [12]. The experience of the Mediterra- nean diet increased the interest in oleic acid (c9-18:1) intake [13]. The interest in increasing the n-3/n-6 ratio of polyunsaturated FA (PUFA) has been confirmed [14]. During the last decade, it has been shown in animal models and/or human cell line cultures that c9t11-CLA, the main natural isomer of conjugated linoleic acids (CLA), and possibly t9t11-CLA, exhibit several interesting fea- tures, especially for the prevention of certain forms of cancer [3, 15–17]. Finally, any evaluation of the effect of dairy products on human health is to be considered in relation to the combined effects of milk FA profile, amount of dairy fat intake, its duration, and interactions between different milk FA as well as between these FA and the rest of the diet (macro- and micronutrients from vegetables, fruits, oils, meat, fish, soft drinks, wine, etc.). Correspondence: Yves Chilliard, URH-TALL, INRA, Theix, F-63122 Saint-GenŠs-Champanelle, France. Phone: 133 4 73624114, Fax: 133 473624519, e-mail: [email protected]ª 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.ejlst.com Review Article
INRA, UR1213 Herbivores,Site de Theix,Saint-Gen�s-Champanelle,France
Diet, rumen biohydrogenation and nutritionalquality of cow and goat milk fat
The potential to modify the milk fatty acid (FA) composition by changing the cow orgoat diets is reviewed. Ruminal biohydrogenation (RBH), combined with mammarylipogenic and D-9 desaturation pathways, considerably modifies the profile of dietaryFA and thus milk composition. The pasture has major effects by decreasing saturatedFA and increasing FA considered as favorable for human health (c9-18:1, 18:3n-3 andc9t11-CLA), compared to winter diets, especially those based on maize silage andconcentrates. Plant lipid supplements have effects similar to pasture, especially lin-seed, but they increase to a larger extent, simultaneously several trans isomers of 18:1and, conjugated or non-conjugated 18:2, especially when added to maize silage orconcentrate-rich diets. The goat responds better for milk 18:3n-3 and c9t11-CLA, andsometimes less for c9-18:1, and is less prone to the RBH trans-11 to trans-10 shift,which has been shown to be time dependent in the cow. The respective physiologicalroles of most milk trans FA have not been studied to date, and more studies in rodentsand humans fed dairy products modified by changing ruminant diet are required beforerecommending a larger use of lipid sources and how to combine themwith the differentfeeding systems used by dairy farmers.
828 DOI 10.1002/ejlt.200700080 Eur. J. Lipid Sci. Technol. 109 (2007) 828–855
1 Introduction
Milk fat secretion and milk fatty acid (FA) composition areof great interest with regard to human nutrition. Apart fromtheir contribution to dairy products’ sensorial quality andto the amount of dietary energy, different lipid and FAcompounds (short- and medium-chain saturated,branched, mono- and polyunsaturated, cis and trans,conjugated FA, etc.) present in ruminant milk fat areindeed potentially positive or negative factors for thehealth of consumers [1–3].
Dairy products provide indeed 25–60% of the overallsaturated fat consumption in Europe, which makes them,since decades, a target of dieticians’ criticism due to thenegative effects of excessive consumption of saturatedFA on human health [4]. The image of saturated FAshould, however, be weighed by the fact that C12–C16
saturated FA are thought to be atherogenic only whenconsumed in excessive amounts, that 18:0 has noatherogenic effect and that saturated fat could even beprotective when compared to a low-fat, high-carbohy-drate diet [5, 6]. The allegedly atherogenic effect of certain
trans monounsaturated FA (MUFA) [7] has not been con-firmed for vaccenic acid (t11-18:1), the main isomerpresent in milk [8, 9]. The intake of some trans isomers of18:2 seems to be particularly harmful, although furtherresearch is needed to discriminate between industrial andruminant isomer profiles [10]. In other respects, it hasbeen shown in humans that the consumption of milk fat[11] could sometimes decrease cardiovascular and/ormetabolic syndrome risk factors. Branched-chain FA,such as iso-15:0, anteiso-15:0 and iso-16:0, have beenshown to present anti-cancer activity in human breastcancer cell models [12]. The experience of the Mediterra-nean diet increased the interest in oleic acid (c9-18:1)intake [13]. The interest in increasing the n-3/n-6 ratio ofpolyunsaturated FA (PUFA) has been confirmed [14].During the last decade, it has been shown in animalmodels and/or human cell line cultures that c9t11-CLA,themain natural isomer of conjugated linoleic acids (CLA),and possibly t9t11-CLA, exhibit several interesting fea-tures, especially for the prevention of certain forms ofcancer [3, 15–17]. Finally, any evaluation of the effect ofdairy products on human health is to be considered inrelation to the combined effects of milk FA profile, amountof dairy fat intake, its duration, and interactions betweendifferent milk FA as well as between these FA and the restof the diet (macro- and micronutrients from vegetables,fruits, oils, meat, fish, soft drinks, wine, etc.).
Eur. J. Lipid Sci. Technol. 109 (2007) 828–855 Feeding factors, rumen biohydrogenation and milk fatty acids 829
Whatever the future conclusions of human nutrition stud-ies on the specific effect of the different milk FA, and theirinteraction with the basal diet, there is a great challengefor scientists working on ruminants to be able to modulatethe milk FA composition. The ruminant milk FA composi-tion is linked to intrinsic (animal species, breed, genotype,pregnancy and lactation stages) or extrinsic (environ-mental) factors [18, 19]. In a given animal species, theeffects linked to breed or genotype are significant butrestricted and they can only be achieved over long terms.The effect of the lactation stage onmilk fat content and FAcomposition is noticeable and mainly linked to body fatmobilization in early lactation [20], but it only lasts a fewweeks each year. Seasonal effects are very large andmainly due to changes in feeding factors.
Nutrition therefore constitutes a natural and economicalway for farmers to markedly and rapidly modulate themilkFA composition. The largest changes can be obtainedeither by changing the forages in the diets of ruminants,particularly pasture, or by adding plant or marine lipidsupplements to the diet (e.g. [19, 21–23]).
The following review pays particular attention to recentstudies on the impact of different diets on the main FAclasses of interest for human nutrition (saturated and cisMUFA, trans MUFA and PUFA, including CLA) in bovineand caprine milk fat. The goat responds very differently todietary factors than the cow, both in milk fat secretion andin some aspects of milk FA composition [24, 25], which isof interest for consumers of caprine dairy products andprovides an interesting model for mechanistic studies onmilk fat secretion and composition. After a short pre-sentation of the digestive and metabolic background, thisreview presents data on the effects on milk FA of foragesources (Section 3) and lipid supplements (Section 4), as
well as forage-concentrate-lipid interactions and persist-ency of milk FA responses (Section 5).
2 Digestion and metabolism of dietary FA
TheFApresent in forages, cereals, andoil seedsaremainly18-carbon PUFA (18:2n-6 and 18:3n-3), whereas some oilseeds are rich in MUFA (mainly c9-18:1) and marine prod-ucts (fish oil, algae, etc.) are rich in long-chain PUFA[mainly 20:5n-3 (EPA) and22:6n-3 (DHA)]. Thesedietary FAare extensively metabolized and biohydrogenated in therumen, resulting not only in the production of 18:0 but alsoa wide range of isomers of PUFA and MUFA, especiallytrans and conjugated FA [26, 27] (Fig. 1). These inter-mediates of ruminal biohydrogenation (RBH) vary largelywith changes in diet composition, as demonstrated bytheir appearance in milk fat under various conditions (e.g.[28–31]). Apart from being absorbed in the gut and directlysecreted into milk, some RBH intermediates are trans-formed by body tissues, especially by themammary gland(Fig. 2) where the D-9 desaturase [stearoyl-CoA desatu-rase (SCD)] acts by adding a cis9-double bond on differentFA [27, 32], which partly reverses the effect of RBH anddecreases the saturation level and themelting point ofmilkfat [33]. Furthermore, RBH intermediates act as regulatorsor disruptors of mammary lipogenesis, which results inchanges in the amount of secreted milk fat but also in milkFA composition (e.g. [34], Shingfield and Griinari, thisissue), including short- and medium-chain de novo syn-thesized FA (Fig. 2). Finally, rumen-escaped dietary PUFAand 18:0 produced in the rumen can be seen as residualprecursors and the end-product of RBH, respectively.Thus, RBHmodifies yields and/or interacts with all milk FAandplays a crucial role in the interaction between ruminantdiet andmammary FA synthesis and secretion.
Fig. 1. Main putative RBH path-ways. When cis or trans configura-tions are not mentioned, it meansthat the various cis-cis, cis-transand trans-trans configurationscould exist. Thick arrows representthe major pathways [26]; thin arrowsrepresent other putative pathways,as suggested by increases in thecorresponding isomers during invitro incubations of pure linoleic andlinolenic acids [46]; dotted arrowsrepresent RBH pathways includingunknown 18:3 isomer inter-mediates. Not all putative FA arementioned, and the numerousinterconversions among 18:1 iso-mers [47, 48] are not represented.
830 Y. Chilliard et al. Eur. J. Lipid Sci. Technol. 109 (2007) 828–855
Fig. 2. Schematic relationships between RBH and milkFA composition. UFA, SFA = unsaturated, saturated FA;Sc, Mc = short-, medium-chain; c9D = cis9-desaturated;[%] = changes in milk FA concentrations (g/100 g totalFA), as a result of changes in the flows of the different FA.
2.1 RBH and lipid digestion
The disappearance of 18:3n-3 and 18:2n-6 in the rumenaverages 93 and 85%, respectively (review [35]). Theextent of RBH depends to a low extent on the amount orthe nature of the lipids in the diet, except when they areprotected against microbial attack [36]. Besides FA trap-ping in vegetable cells, the main factor in the variation ofRBH is the percentage of concentrate in the diet. Dietscontaining more than 70% concentrates strongly reduceRBH [37–39]. This is probably due to a low pH, which hasbeen shown to limit the rate of lipolysis [40] and, for lino-leic acid, the isomerization and the second reduction,leading to the accumulation of vaccenic acid [41].
Although Harfoot and Hazlewood [26] described only alimited number of pathways that result in a small numberof isomers, it has long been known [42] that rumendigesta and bacteria contain a wide variety of cis- andtrans-18:1 isomers (Fig. 1). Several isomers of CLA werealso described. Specific isomers can be associated todietary PUFA: 18:3n-3 metabolism results in the produc-tion of a series of intermediates (mainly c9t11c15-18:3,t9t12t15-18:3, t11c15-18:2, t11t13-CLA, t11c13-CLA,t11-18:1, t13-18:1) whereas 18:2n-6 metabolism resultsin the production of 8,10-CLA, 9,11-CLA, t10c12:CLA andmainly t10-18:1. This has been shown in vivo with lipidsupply from linseed or sunflower [39, 43, 44], and morespecifically in vitrowith pure FA [45, 46]. Using labeled c9-18:1 and t9-18:1, it has been shown that these FA may beconverted into a large number of 18:1 isomers [47, 48].Besides the nature of dietary FA, the diet composition is amajor determinant of the composition of RBH inter-
mediates. A high proportion of concentrates together withan 18:2n-6 supply results in a shift of t11-18:1 to t10-18:1in the rumen [39, 49].
Dietary polyunsaturated 20- and 22-carbon FA as EPAand DHA are extensively biohydrogenated and result in alarge number of unsaturated FA and a small number ofsaturated FA [50, 51]. In addition, these FA inhibit the RBHof 18-carbon (C18) PUFA [52, 53].
CLA are present in very small amounts in digestive con-tents (less than 0.5% of total FA). This low concentrationis due to rapid biohydrogenation, and c9t11-CLA alwaysrepresent less than half the total CLA. The t10c12 isomeris generally either undetectable or present in very smallamounts (e.g. [39, 49]).
2.2 Duodenum-plasma-milk relationships
Most FA reaching the duodenum are unesterified. Theyare absorbed in the intestine and can be D-9 desaturatedin the enterocyte [54], but only to a limited extent. Theyare then esterified in the enterocyte and exported to theother organs as chylomicrons and very-low-density lipo-proteins. When duodenum and plasma total FA profilesare compared, the essential and non-essential FA differ:proportions of 18:2n-6 and 18:3n-3 are largely higher inplasma and their proportions are only remotely linked totheir amount in the duodenum [55]. As a consequence,non-essential FA such as trans-18:1 and several 18:2isomers have lower proportions in plasma FA than theirproportions in duodenum FA, but there are close linearrelationships between plasma and duodenal proportions.The profile of total plasma FA reflects a mean of severallipid classes differing substantially in their FA profile andmetabolism. Thus, FA profiles of triacylglycerols and freeFA (the main sources of plasma FA for the mammarygland) are richer in 18:0 and c9-18:1 [56, 57], with a com-position close to duodenal FA [39, 43], whereas phos-pholipids and cholesterol esters (not significantly used bythe mammary gland [58]) are very rich in 18:2n-6 and18:3n-3, with a profile largely different from that of duo-denal FA.
The difference between essential and non-essential FAobserved in the comparison between duodenum andplasma FA in cows also applies for the comparison be-tween plasma and milk FA, both in cows and goats(Tab. 1). Regarding the proportions of the main 18-carbonFA in plasma and milk, measured on 25 cows and84 goats in three experiments with lipid-supplemented orcontrol diets, the plasma-milk relationships are linear, withhigh R2 (.0.80) and high slopes (.1.26) for t10-, t11-,t13114-18:1, t11c15- and c9t11-CLA. By contrast, for
Eur. J. Lipid Sci. Technol. 109 (2007) 828–855 Feeding factors, rumen biohydrogenation and milk fatty acids 831
Tab. 1. Relationships between proportions of selected trans-18:1 and polyunsaturated FA in cowand goat milk (y) as a function of their proportion in plasma (x). FA proportions are expressed in g/100 g total FA. Equations are linear regressions across 25 individual measurements from cowsreceiving seven control or lipid-supplemented diets in two experiments (calculated from [29, 39, 43,59]), and 84 goats receiving seven different control or lipid-supplemented diets (described in Tab. 6,trial E) (A. Ferlay, J. Rouel, Y. Chilliard, unpublished results).
FA Meanproportionin plasma (x)
Meanproportionin milk (y)
Milk/plasmaratio (y/x)
Equation r2
Cowc9t11-CLA 0.22 1.70 7.7 y = 6.69x 1 0.21 0.81t10-18:1 0.52 2.58 5.0 y = 4.95x 1 0.01 0.93c9t13-18:2 0.12 0.46 3.8 y = 2.98x 1 0.09 0.61t11c15-18:2 0.37 1.28 3.5 y = 2.90x 1 0.20 0.96t11-18:1 1.99 3.73 1.9 y = 1.50x 1 0.74 0.86t13114-18:1 0.78 1.34 1.7 y = 2.48x – 0.58 0.8918:3n-3 9.33 1.00 0.11 y = 0.06x 1 0.40 0.3818:2n-6 42.10 2.22 0.05 y = 0.08x 2 1.19 0.48
Goatc9t11-CLA 0.79 2.34 3.0 y = 2.42x 1 0.44 0.83c9t13-18:2 0.23 0.41 2.0 y = 1.48x 1 0.07 0.72t11c15-18:2 0.53 1.35 2.8 y = 2.18x 1 0.20 0.87t11-18:1 4.28 5.69 1.3 y = 1.26x 1 0.29 0.9118:3n-3 6.00 1.28 0.22 y = 0.23x 2 0.13 0.8918:2n-6 24.65 2.07 0.09 y = 0.09x 2 0.07 0.55
18:2n-6 the relationships are not as close, with R2 ,0.56and slopes ,0.10. For 18:3n-3, the relationships differ alittle bit between the goat (high R2 = 0.89 and slope= 0.23) and the cow (R2 = 0.38 and slope = 0.06). The dif-ferences between essential and non-essential FA areprobably a consequence of the metabolism of the differ-ent FA pools in plasma (see above) and sparing essentialFA for essential biological functions.
When calculating the transfer efficiencies of trans-18:1and non-conjugated PUFA from duodenum to milk inFigs. 3 and 4, mean values are similar among the differentFA. However, they differ largely between diets, with highvalues (62–71%) when milk fat content is regular (33–34 g/kg, with the two high-forage diets) and low values(24–44%) when milk fat content is low (22–27 g/kg, withthe five low-forage diets). This could be explained [55] bythe fact that the mammary 18-carbon FA uptake andsecretion was limited when de novo FA synthesis wasdecreased by milk fat-depressing diets (see Sections 3–5). Nevertheless, when one compares the profiles ofduodenum and milk 18-carbon FA, the relations are veryclose for all FA, both essential and non-essential [55]. Asan example, there is a close linear relationship betweenthe proportion of t11-18:1 in 18-carbon FA at the duode-num and its proportion in milk 18-carbon FA, with a slopeof 0.73 (Fig. 5). The proportion of c9t11-CLA in milk is also
closely related to the proportion of t11-18:1 in the duo-denum, illustrating the post-ruminal origin of most c9t11-CLA, i.e. from mammary desaturation of t11-18:1 of diet-ary origin [27, 51, 55, 59]. The ratio of the two slopesequals 0.44, which is close to the 0.38–0.43 c9t11-CLA/t11-18:1 ratio in cow milk [60–62]. The similarity of the C18
profiles between duodenum and milk is also exemplifiedin Figs. 3 and 4. The pattern of the duodenal flows oftrans-18:1 differs according to dietary factors (source ofadded lipids in this case [39, 43]), i.e.mainly t11- and t13-to t16-18:1 for linseed oil supplementation versus mainlyt10- and t11-18:1 for sunflower oil- and fish oil-supple-mented diets. These differences are closely reflected inthe pattern of milk FA secretion. The similarity betweenduodenum and milk FA patterns also applies to PUFA,except c9t11-CLA which is largely synthesized in themammary gland from t11-18:1 uptake (Figs. 3–5). In thecomparison between duodenum and milk FA, the differ-ential behavior between essential and non-essential FAobserved for plasma does not exist: for a similar forage/concentrate ratio, secretion of 18:2n-6, t11c15-18:2 and18:3n-3 in milk is proportional to duodenal flow [55].
The different behaviors of essential FA somewhat confusethe similarity between plasma and duodenal FA profiles,and thus in particular the putative use of plasma profilesas a predictor of duodenal profiles. This does not
Eur. J. Lipid Sci. Technol. 109 (2007) 828–855 Feeding factors, rumen biohydrogenation and milk fatty acids 833
Fig. 5. Concentrations of t11-18:1 and c9t11-CLA in cowmilk 18-carbon FA as a function of t11-18:1 concentrationin duodenum 18-carbon FA (regression lines with nullintercepts). Data points are individual cow measurementsfrom two experiments (n = 25) (calculated from [29, 39,43, 59]).
seem to be the case for milk FA profiles, which could beused to predict the modifications of duodenal FA profilesinduced by dietary conditions.
2.3 Effects of RBH intermediates on mammarylipogenesis
Milk fat is composed of ca. 98% triacylglycerols (in whichFA represent ca. 95%), less than 1%of phospholipids andsmall amounts of cholesterol, 1,2-diacylglycerols, mono-acylglycerols and free FA [2]. Milk FA are either de novosynthesized in the mammary gland (almost all 4:0–14:0and ca. 50% of 16:0) or extracted from the arterial blood(reviews [33, 63]). Furthermore, C10–C19 may be D-9-desaturated by the SCD, resulting in particular in palmi-toleoyl-CoA, the major part (70–95%) of bovine milkc9t11-CLA [51, 59, 64, 65] and t7c9-CLA [66] and mainlyoleyl-CoA [67, 68]. Finally, these FA are esterified to glyc-erol and the triacylglycerols are secreted as milk fat glo-bules.
These different lipogenic pathways are regulated in partby long-chain FA (including MUFA and PUFA) originatingeither from dietary FA absorption or from body fat mobili-zation, which decrease de novo FA synthesis [20, 69, 70].Furthermore, a crucial role has been proposed recentlyfor trans FA in milk fat depression ([34], Shingfield andGriinari, this issue). These FA are linked to alterations inPUFA RBH, especially t10-18:1 and t10c12-CLA whichincrease due to an alternative pathway for RBH of 18:2n-6, when rumen pH decreases. A curvilinear relationshipbetween milk fat depression and small increases in milkt10c12-CLA was indeed observed in some studies [30,
34, 71, 73] but not in others [29, 72]. An inhibitory effect oft10c12-CLA onmilk fat synthesis andmammary lipogenicgene expression was demonstrated by duodenal infusionin dairy cows [74]. However, in nutritional studies, thelevels of t10c12-CLA in the rumen, duodenal fluid or milkalways remained very low compared to the levels used ininfusion studies, whereas t10-18:1 levels were muchhigher [29, 34, 39, 75, 76]. Furthermore, curvilinear rela-tionships occurred between milk t10-18:1 and fat yieldresponses (e.g. [29, 30], Shingfield and Griinari, thisissue).
Nevertheless, postruminal infusion of 43 g t10-18:1/day/cow over 4 days had no effect on milk fat synthesis [77].Although in some trials the duodenal flow or milk con-centration of t10-18:1 can be more than twice (Fig. 3) or16 times higher [30], respectively, than in the study by Locket al. [77], it is likely that the formation of t10-18:1 andt10c12-CLA is accompaniedby the formation of otherRBHintermediates that could also inhibit (or co-inhibit witht10c12-CLA) milk fat synthesis. Indeed, in nutritional stud-ies, several trans-18:1 and 18:2 isomers vary simulta-neously and exhibit high negative correlations with milk fatcontent and secretion (e.g. [29–31, 78]). Furthermore, fivedifferent CLA isomers have been post-ruminally infusedintocows (reviewShingfieldandGriinari, this issue). Amongthem, only c10t12-CLA [79] and t9c11-CLA [80] reducedmilk fat synthesis. However, the relative efficiency ofinfused t9c11-CLAwas lower than that of t10c12-CLA [80],which is in agreement with regression lines observed be-tween milk fat secretion and the concentration of theseisomers inmilk fat in cow feeding trials [30, 31].
Another mechanism linked to RBH putatively regulatingmilk fat depression is the decrease in 18:0 availability formammary c9-18:1 synthesis that occurs when PUFA-richoils, in particular marine oils, inhibit the last step(s) oftrans-18:1 isomer hydrogenation ([29, 31, 81], Shingfieldand Griinari, this issue).
In the goat, nearly all types of lipid supplements added toa large variety of basal diets induce a sharp increase inmilk fat content [24, 25], in contrast to the cow. This islikely due to a lower ruminal yield of t10-18:1 and asso-ciated isomers (see Section 5) combined with the factthat the mammary lipogenesis seems much less respon-sive to post-ruminally infused t10c12-CLA [82]. In otherrespects, the effects of dietary lipids on mammary SCDgene expression differ markedly between cows and goats(review [68]). These differences could be partly explainedby factors linked to the diet (e.g. level of starch) and thenature and presentation of the lipid supplements, but alsoto species differences observed in milk C18-D-9 desa-turation ratio responses (see Section 4) and/or to a higher18:3n-3 and 18:2n-6 milk/plasma ratio in goats (Tab. 1).
834 Y. Chilliard et al. Eur. J. Lipid Sci. Technol. 109 (2007) 828–855
3 Effects of forage source on milk FA
3.1 Cow milk
3.1.1 Effects of pasture
Fresh grass dry matter (DM) contains 1–3% FA, with thehighest values during spring and autumn, and about 50–75% of these FA as 18:3n-3 [83, 84]. Compared to mixedwinter diets, pasture increases milk fat concentrations of18:0 (12 g/100 g FA), 18:1 (18), 18:3 (11.0) and CLA(10.6) and decreases 10:0–16:0 (–13) (reviews [21, 85]).
This has been confirmed and defined over the last5 years. Milk fat c9-18:1 is higher on pasture than withhigh-forage winter diets (22–24 vs. 15–18 g/100 g FA,Fig. 6), despite the grass being low in c9-18:1 [86]. Thisresult could be explained by the higher 18:3n-3 intake onpasture, resulting, after RBH, in higher 18:0 absorptionand mammary D-9 desaturation. From six direct compar-isons between grass pasture and mixed winter diets(review [23]), it can be calculated that pasture significantlyincreases (p ,0.05) milk fat concentrations of 18:3n-3and CLA (10.5 and 10.9 g/100 g FA, respectively). Otherstudies showed that pasture, compared to either maizesilage [87] or total mixed rations ([88–91] and review [92]),increases t11-18:1, c9t11-CLA and 18:3n-3 (and some-times 15:0, 17:0 and c9-18:1) and decreases 16:0 (andsometimes 8:0–14:0 and 18:2n-6). Inconsistent resultswere observed across studies on 4:0, 6:0 and 18:0.
When the pasture percentage increases in the total diet,linear increases in 18:3n-3, t11-18:1 and c9t11-CLA anddecreases in 10:0–16:0 are observed. Thus, when pastureincreased from 33 to 100% of the diet, 18:3n-3 and c9t11-CLA each increased from 0.8–0.9 to 2.0–2.2 g/100 g FA[93] or from 0.4 to 0.7 (18:3n-3) and 0.5 to 1.6 (c9, t11-CLA) [94]. The very consistent effects of pasture on 18:3n-3,t11-18:1 and c9t11-CLA are related to the high content of
18:3n-3 in most pastures, which is partly biohy-drogenated into t11-18:1 and partly absorbed intact in thegut and secreted into milk. Consistent with this, pasturemilk is richer in t11c15-18:2 (an intermediate of RBH of18:3n-3) than winter milk (0.5–0.8 vs. ,0.1 g/100 g FA[84]). However, pasture milk 18:3n-3 and c9t11-CLA arefrequently lower than 0.7 and 1.1 g/100 g FA, respectively([86, 90, 95] and reviews [21, 23, 85]). This is likely due tothe decrease in FA and 18:3n-3 contents in mature com-pared to young growing grass [23], in agreement with theobservation that milk concentrations of 18:0, c9-18:1,t11-18:1, c9t11-CLA and 18:3n-3 are much higher at 3 wkthan 6 wk after turning out to pasture ([86] and Fig. 6).However, temporal adaptation in rumen or mammarymetabolism could also occur (see Section 5) and con-tribute to such changes.
Dewhurst et al. [23] reviewed six direct comparisons be-tween milk produced during the summer, either on alpinepastures or in lowland conditions (either on pasture orwith conserved forages and concentrates). It can be cal-culated from this review and from Lucas et al. [96] thatalpine milk is significantly richer in c9-18:1 (13.8 g/100 gFA), t10111-18:1 (12.6), CLA (11.3) and 18:3n-3 (10.8),and poorer in 12:0 (–0.9), 14:0 (–1.9) and 16:0 (–6.0)(Tab. 2). Furthermore, c9t11-CLA and 18:3n-3 decreasedin a field survey in the order: alpine pasture . permanentgrassland pasture of first use . second use . temporarypasture . grass silage . hay . maize silage [96]. Quickchanges (a few days) were observed after either turningout to pasture or transition from fresh grass to a silage diet[21, 97].
High c9-18:1 and 18:3n-3 concentrations in alpine milkare observed despite the fact that there is not always ahigh content of these two FA in the alpine pastures. Leiberet al. [98] suggested that this may be related to otherbotanical components that could reduce RBH and/
Fig. 6. Effects of forage source on oleic, rumenic and linolenic acid concentrations (g/100 g total FA) of cow milk fat(adapted from [86]). CB, concentrate-based diet. High-forage diets: MS, maize silage; H, hay; NG, natural grassland;P, pasture at 3 or 6 (n ) weeks after beginning of pasture; RG, rye-grass; S, silage.
Eur. J. Lipid Sci. Technol. 109 (2007) 828–855 Feeding factors, rumen biohydrogenation and milk fatty acids 835
Tab. 2. Effects of Alpine grazing compared to Lowlandconditions (pasture or mixed diets) on cow milk FA com-position (calculated from Lucas et al. [96] and six studiesreviewed by Dewhurst et al. [23]).
*,**,*** Significantly different from zero (p ,0.05, 0.01,0.001, respectively; paired t-test).
or, in the case of c9-18:1, to higher use of adipose FA dueto alpine pasture conditions. Furthermore, alpine milk isrich in odd- and branched-FA, in t11c15-18:2, in t11t13-CLA and particularly in t11c13-CLA, which is the secondmost important CLA isomer (after c9t11-CLA) in this typeof milk [28, 99]. These 18:2 and CLA isomers are indeedproduced during 18:3n-3 RBH (Fig. 1). However, t8c10-CLA, which is probably produced during 18:2n-6 RBH, isalso increased [99].
3.1.2 Effects of conserved forages
3.1.2.1 Hay and grass silage
Wilting during hay making (and to some extent prior toensiling) is associated with decreases in grass FA and18:3n-3 concentrations due to oxidative loss as well as toleaf shatter during hay making since leaves contain moreFA than stems [23]. This results in lower (up to –75%)concentrations of 18:3n-3 in hay compared to grasssilage [100–102]. Furthermore, grass is generally har-vested later for making hay than silage, which couldinteract as an effect of the physiological stage of grass todecrease hay 18:3n-3.
However, milk from cows receiving hay can be richer in18:2n-6 and 18:3n-3 compared to grass silage feeding,despite much lower intake of these two FA, because theyhave much higher transfer efficiencies from diet to milkwith hay (29 and 17%) than with silage (15 and 3%,respectively) [102]. This observation may be related to thefact that in sheep RBH was lower for hay than for freshgrass or grass silage [101] and that ensiling produces a
release of free FA from grass acylglycerols [103]. Severalstudies in the 1970s also showed high milk 18:3n-3 con-centrations when cows were fed hay (review [21]) and thiswas confirmed by a meta-analysis comparing milks fromfive hay-fed to ten grass silage-fed cow groups, having0.99 vs. 0.43 g 18:3/100 g FA (p ,0.001) (F. Glasser, A.Ferlay, Y. Chilliard, unpublished). Furthermore, when hayis dried in the barn in order to limit wilting losses, its18:3n-3 concentration is high and enables the yield ofmilks with similar or higher 18:3n-3 concentrations thanpasture and higher t11-18:1 and c9t11-CLA concentra-tions than grass silage (Fig. 6). A direct comparison ofwrapped haylage (51% DM) with grass silage (39% DM)made from the same grassland showed only marginalchanges in milk FA composition [104]. Silage preparedfrom semi-natural grassland resulted in slightly highermilk concentrations of t11-18:1, c9t11-CLA, 18:2n-6 and18:3n-3 compared with botanical species-poor, inten-sively managed grassland [105]. Overall, any differencesin FA profiles between milks coming from either hay- orgrass silage-based diets would be of limited magnitude.
3.1.2.2 Legume silage
It can be calculated from the review of Dewhurst et al. [23]that, in six direct comparisons with grass silage (four trialsusing red clover and two white clover), legume silageincreases milk 18:2n-6 and 18:3n-3 by 0.4 and 0.6 g/100 g FA, respectively. These authors explain that thisresult may be due to legumes being rich in these PUFA(white clover especially in 18:3n-3); the transfer efficiencyof 18:3n-3 from diet to milk being higher with red clovercompared to grass silage (9 vs. 4.5%); passage ratethrough the rumen being higher for white clover; and redclover having a much lower lipolysis in the rumen thangrass due to its polyphenol oxidase activity.
Milk from organic farming is richer in 18:3n-3 than milkfrom conventional farming, whereas a difference in c9t11-CLA is less consistently observed [28, 106, 107]. This highconcentration in 18:3n-3 is very likely related to the largeruse of legume plants in organic farming. Furthermore, inone study, organic milk was richer in several trans-18:1isomers (mainly t13-18:1, but not t10-18:1) and in severalminor CLA isomers [28]. This observation deserves fur-ther research on a larger scale to be confirmed and tounderstand its putative causes.
3.1.2.3 Maize silage
Maize silage (which generally contains 30–40% grain) isrich in 18:2n-6 and c9-18:1, and poor in 18:3n-3. This mayexplain why feeding maize silage (six trials with .60%
836 Y. Chilliard et al. Eur. J. Lipid Sci. Technol. 109 (2007) 828–855
maize silage) compared to grass silage (five trials with.58% grass silage) sharply increased the milk n-6/n-3ratio; however, 18:0 and total 18:1 did not change (review[21]). This was confirmed by direct comparisons which,moreover, showed no change in t11-18:1 and c9t11-CLA,and a slight decrease or no change in 18:0 and c9-18:1when replacing grass silage with maize silage in medium-concentrate (Tab. 3) or low-concentrate (Fig. 6) diets,respectively. Compared to a hay-based diet, a diet rich inmaize silage and concentrates decreased milk fat con-centrations in branched-chain FA, t11c15-18:2, t11c13-CLA, t11t13-CLA, t12t14-CLA and increased c11-18:1,c12-18:1, t7c9-CLA, t8c10-CLA, t9c11-CLA and t10c12-CLA [30]. Part of these decreasing or increasing isomersare RBH intermediates of 18:3n-3 or 18:2n-6, respectively(see Fig. 1 and Section 4) and likely result from dietary FAdifferences.
3.1.3 Effect of forage/concentrate ratio
The effect of increasing the concentrate percentage in thediet on milk fat content is dependent on the range ofincrease: when the concentrate does not exceed 50–60%of the diet, the milk fat content does not vary largely,whereas a strong decrease is generally observed above
60% [22, 108, 109]. The effects on milk FA compositionalso largely differ according to the range of concentratepercentage variation: in a trial on pasture with con-centrate increasing from 3 to 35% [110, 111], the maineffects were to increase milk fat concentrations of 4:0–14:0, trans-18:1 isomers (except t11-18:1) and 18:2n-6,and to decrease c9-18:1, t11-18:1, c9t11-CLA and 18:3n-3. By contrast, in a trial using grass hay with concentrateincreasing from 36 to 66% [29], the main effects were toincrease milk fat concentrations of all trans-18:1 isomers(particularly t10-18:1), c9t11-CLA and 18:2n-6, and todecrease 14:0, 16:0, and 18:0 (Tab. 4). Similar trends wereobserved in other studies, either in the low range of con-centrate percentages with diets based on grass orlegume silages [112] or in the high range with diets basedon maize silage and alfalfa haylage [38, 49]. In otherrespects, increasing the dietary concentrate percentagefrom 20 to 70% (or increasing maize silage) decreasedmilk odd- and branched-chain FA, with a clear linear de-crease in the ratio of odd-chain iso-FA to anteiso-FA(review [113]).
Thus, it seems that increasing the concentrate intake inthe low range favors both milk 18:2n-6 and mammary denovo FA synthesis despite a shift in RBH towards moretrans-18:1 isomers, at the expense of 18:3n-3 and c9t11-
Tab. 3. Effect of forage source, and source and amount of oil supplement on milk yield, fat content and FA composition (g/100 g total FA) (A. Ferlay, Y. Chilliard, unpublished data).{
{ 20 cows were used in two replicated 565 Latin Square designs with 3-week periods.{SO, sunflower oil (18:2n-6 rich); LO, linseed oil (18:3n-3 rich).§ ALA, alpha-linolenic acid (18:3n-3); LA, linoleic acid (18:2n-6).# Diet containing 60% maize silage, 5% grass hay and 35% concentrates.{{Diet containing 47% grass silage, 13% grass hay and 40% concentrates.{{Significant effect at p ,0.01, 0.05 or 0.10. Interactions were significant (p ,0.10) for milk yield (oil-amount), fat content(forage-amount), 18:0, t10111-18:1, 18:2n-6, 18:3n-3 (forage-oil), 18:2n-6 and ALA/LA (oil-amount) and 18:3n-3 and ALA/LA (forage-amount).
{ LC, MC, HC = low-, medium-, high-concentrate diet.{High allowance of grass pasture (adapted from Bargo etal. [110, 111]).§ Adapted from Loor et al. [29].
CLA. On the other hand, increasing the concentrate in thehigh range clearly orients RBH to the t10-pathway,resulting in milk fat depression and a milk rich in trans-FAand 18:2n-6 (in agreement with observed duodenal flows[39, 49] and Figs. 3, 4) and poor in 14:0–18:0. However,increasing the concentrate in the high range did not resultin similar responses when it was added to a diet whereunsaturated FA were replaced by saturated ones [114],showing that important interactions exist between theeffects of the starch, fiber and lipid components of thecow diet (see Section 5).
The starch source itself may also change RBH and milkFA composition. Thus, simply replacing wheat (rapidlydegradable starch) with potatoes (slowly degradable)(both at 30% of the diet) increased ruminal pH and milkconcentrations of 4:0–16:0 and decreased c9-18:1 andtrans-18:1 (mainly t10-18:1, –1.5 g/100 g FA) [115].
3.2 Goat milk
Grazing mountain spring pasture, compared to winterdiets (alfalfa hay, straw and concentrates), increased goatmilk fat 18:3n-3 (10.5 g/100 g FA) without changingc9t11-CLA [116]. Zero-grazing fresh rye-grass, comparedto a rye-grass hay-based diet, did not change 18:3n-3
and c9t11-CLA and increased c9-18:1 (Tab. 5), whereassmall but significant decreases were observed for 11:0–14:0, c9-14:1, 16:1, c9-17:1 and odd- and branched-chain FA [117].
Compared to rye-grass hay, alfalfa hay decreased 14:0,c9-14:1, 16:1 and odd- and branched-chain FA andincreased 20:0–24:00, 18:2n-6, 18:3n-3 (10.3 g/100 gFA), EPA and the 18:3n-3/18:2n-6 ratio ([117] and Tab. 5,trial B). Dehydrated alfalfa, richer in lipids and 18:3n-3,increased milk fat 18:0, t11-18:1 and 18:3n-3, comparedto alfalfa hay [118].
Increasing the concentrate percentage in the diet (alfalfahay-based diets) from 32–33 to 56–67 decreased 16:0,18:3n-3 (–0.3 g/100 g FA) and the 18:3n-3/18:2n-6 ratio,and increased 10:0–14:0, 18:2n-6, t11-18:1, c9t11-CLAand other trans FA ([19] and Tab. 6). Similar trends wereobserved when comparing total mixed rations containing55–60 vs. 30–35% forage [118, 119]. Compared to alfalfahay, maize silage decreased 16:0, odd- and branched-chain FA, 18:2n-6, 18:3n-3 (–0.3 g/100 g FA) and the18:3n-3/18:2n-6 ratio, and increased 18:0 ([120] andTab. 5, trial A).
Altogether, the differences observed in goat milk FA dueto the forage source and the forage/concentrate ratio areconsistent with the results in cows. These effects are,however, of small magnitude, especially when comparedto the effects of lipid supplementation (see Sections 4and 5). The main effect was a consistently higher milk18:3n-3 concentration with good-quality alfalfa hay-based diets, or on pasture, while increasing concentratesor maize silage had the opposite effect.
4 Effects of lipid supplements on milk FA
Feeding lipid supplements to dairy ruminants has beenused widely for decades by researchers and, to someextent, by farmers to modify dairy performance andenergy metabolism (reviews [22, 121]) and/or milk FAcomposition (reviews [4, 18, 25, 33]). Both the sourceand presentation form of the lipids influence theireffects. Attempts to change the proportion of one cate-gory of FA often induce changes in other FA, which maybe considered positive or negative for consumer health.Thus, diets that decrease milk saturated FA andincrease PUFA and/or CLA generally result in highertrans-18:1 proportions, the effects of which are stillcontroversial [8, 9, 122]. In other respects, using medi-um-to-high levels of lipid supplementation can some-times change dairy performance (feed intake, milk yieldand/or protein and fat content) and thus economicprofitability for the farmers.
840 Y. Chilliard et al. Eur. J. Lipid Sci. Technol. 109 (2007) 828–855
4.1 Cow milk
4.1.1 Saturated FA and oleic acid
The potential to decrease medium-chain saturated FA(10:0–16:0) is great. For example, with hay-based diets,these four FA represented 56% of cow milk fat anddecreased to 29% after linseed oil (5% of diet DM) sup-plementation [30]. Conversely, if lipid supplements arerich in medium-chain FA, these could be increased. Suchis the case with palm oil calcium salts, which increasepalmitic acid concentration (12.1 g/100 g FA, for 762 g/day mean supplementation over six trials; [123, 124] andreview [125]). Furthermore, intake of 476 g/day of palm oilFA (containing 87% 16:0) increased milk 16:0 concentra-tion by 8.4 g/100 g FA [126].
Contrary to medium-chain FA, milk short-chain FA con-centrations (4:0, 6:0 and, to a lesser extent, 8:0) are notchanged, either by body lipid mobilization [20] or plant ormarine oil duodenal infusions (review [33]). That specific-ity is probably due to the fact that these FA are partlysynthesized by metabolic pathways not dependent onacetyl-CoA carboxylase [127]. However, 6:0 and 8:0 areslightly reduced by lipid supplementation in the diet(review [19]), probably because trans and conjugated FAcoming from RBH are more potent than other FA in inhi-biting lipogenic pathways.
Odd- and branched-chain FA concentrations aredecreased by 18:2n-6 or 18:3n-3 supplementation,whereas the opposite effect is observed with fish oil sup-plementation, which decreased even-chain iso-FA butmarkedly increased iso-17:0, likely due to specific effectson fiber ruminal digestion (review [113]).
Stearic acid secretion in milk can be increased either bydietary 18:0 intake or by supplementation of 18-carbonunsaturated FA [29, 99, 128] because they are in large parthydrogenated to 18:0 in the rumen [39, 43]. Similarly, oleicacid secretion can be increased either through its directgut absorption and mammary secretion or mainly (ca.80% [55]) from its RBH followed by mammary desatura-tion of 18:0. Another way to increase milk c9-18:1 secre-tion is the distribution of oleamides [36, 129, 130].
Tallow supplementation (rich in 16:0, 18:0 and c9-18:1)sharply increases milk fat 18:0 and 18:1 and reduces10:0–14:0 ([131] and review [21]), although few data areavailable on its putative effects on trans-18:1 [132]. How-ever, most of these supplements have a bad image inEurope since the BSE crisis and the banning of animalprotein sources for feeding ruminants.
When feeding unprotected vegetable oils or seeds con-taining high levels of c9-18:1, 18:2n-6 or 18:3n-3, the
proportions of both 18:0 and c9-18:1 are increased inmilk. For example, cow’s milk c9-18:1 concentration wasincreased 1.18–1.35 times in a dose-dependent waywhen adding either linseed or sunflower oil to the diet(Tab. 3). Positive and variable responses of c9-18:1 or cis-18:1 were also observed when feeding rapeseed oil(1.33–1.67 times), rapeseeds (1.92 times), high-oleicsunflower oil (1.27 times), soybean oil (1.22 times),extruded soybeans (1.17 times), linseed oil (1.26–1.80times) or linseeds (1.22 times) (reviews [4, 23]).
By contrast, fish oil intake does not clearly change 4:0–16:0 but sharply decreases milk 18:0 and c9-18:1 con-centrations (reviews [4, 21]) due to the inhibition of the laststep of RBH which results in a high production of ruminaland milk t11-18:1 at the expense of 18:0.
4.1.2 Polyunsaturated FA
Essential PUFA are not synthesized by tissues in rumi-nants, so their concentration in milk is closely related tothe quantities absorbed in the intestine and hence todietary PUFA intake and to the proportion of that escap-ing RBH (see Section 2.1).
4.1.2.1 Linoleic acid (n-6 series)
In the absence of supplementary lipids, the proportion of18:2n-6 in milk FA is between 2 and 3%. When rations aresupplemented with 18:2n-6-rich seeds or oils like soy-bean or sunflower, this proportion rarely exceeds controlvalues by more than 1.5% (reviews [19, 23] and Tab. 3).However, higher increases were observed using eitherextruded soybeans (11.9 g/100 g FA [133]), micronizedsoybeans (12.4 g/100 g FA [134]), butylsoyamide(12.7 g/100 g FA [135]), or roasted soybeans (13.0 g/100 g FA [136]).
It has often been suggested that giving lipids in the formof seeds rather than oil would limit RBH because seedhulls would restrict bacterial access to lipids. However,rapeseed hulls appear to have a less protective effectthan soybean or sunflower hulls on milk fat content and18:2n-6 percentage in cows fed these respective seeds[4, 19]. Furthermore, when added to a maize silage diet,crushed raw soybean or rapeseeds decreased milk fatcontent (–10 g/kg) and yield of 4:0–16:0 to the sameextent as their respective oils given in free form with oilmeals [137]. Additional research is necessary to confirmthese trends in a larger number of direct comparisonsbetween oil and seeds.
Direct comparison showed that extruded soybeanincreased less 18:2n-6 than raw or micronized soybean
Eur. J. Lipid Sci. Technol. 109 (2007) 828–855 Feeding factors, rumen biohydrogenation and milk fatty acids 841
[138, 139], probably because extrusion enhanced the oilrelease from vegetable structures, enhancing their RBH.However, opposite results were obtained for sunflowerseeds [140] and rapeseeds [141], for which extrusionincreased milk 18:2n-6.
Lipid supplements can be protected from RBH byencapsulating them in a tanned-protein layer. Amounts of15–20% of 18:2n-6 in milk FA have been reached withencapsulated soybean, rapeseed, cotton, safflower orsunflower oil supplements [142]. The limitations of such adietary practice are linked to the processing costs and tothe controversial use of formaldehyde. Other so-calledlipid protection techniques, such as FA salts, do not pre-vent PUFA hydrogenation or the negative effect of rape-seed oil on milk fat content ([143] and review [19]) be-cause the salts are dissociated in the rumen as the pHdecreases. Lastly, it is worth remembering that increasingthe 18:2n-6 proportion in dairy products is not a target initself, insofar as improving the nutritional value of theseproducts preferably requires increasing the 18:3n-3/18:2n-6 ratio.
4.1.2.2 Linolenic acid and long-chain n-3 FA
Apart from grass and some legumes, linseed is the onlyoilseed easily available in Europe which provides veryhigh 18:3n-3 levels, representing more than 50% of FA.Rapeseed contains ca. 7% of 18:3n-3, some of which isprobably secreted in milk. However, as noted with 18:2n-6, rapeseed oil or seed addition does not significantlyincrease milk 18:3n-3 (reviews [4, 19]). Soybean lipidscontain ca. 8% of 18:3n-3 and enables milk 18:3 to beincreased (10.6–0.7 g/100 g FA) when roasted [136] ormicronized [134].
Few trials have been conducted, where cows’ diets weresupplemented with linseed oil or raw seeds. Among sixolder studies, two found no increase and four foundincreases in milk 18:3n-3 in the range of 10.3 to 10.8 g/100 g FA (review [19]). Among seven other studies, thesame range (0.3–0.9) of increase was observed [29, 30,62, 99, 128, 134, 144]. Formaldehyde treatment of lin-seeds did not increase milk 18:3n-3 more than raw seedsdid [145, 146]. Furthermore, the intake of 200–460 g/dayof 18:3n-3 from extruded linseeds [128, 144, 147, 148] orextruded rapeseeds 1 linseeds [149] increased the cowmilk fat 18:3n-3 percentage by 0.3–0.9 g/100 g FA, i.e. inthe range observed above with unprocessed linseeds oroil and lower than what could be obtained with grazinghigh-quality pastures (see Section 3.1.1.).
The variability of the published results requires new stud-ies that discriminate between the effects of oil and seeds
and those of seed processing in particular. However, thepotential to increase milk 18:3n-3 seems to be limitedeven when high doses of supplementation are used.Thus, when the linseed oil amount was increased fromzero to 1.5 and 3.0% of diet DM, the 18:3n-3 response inmilk was not increased proportionally to the oil intake(Tab. 3), and increasing xylose-treated, whole crackedlinseeds from 8 to 21% of the diet only slightly increasedmilk 18:3n-3 (10.5 g/100 g FA) [150].
The secretion of long-chain FA of the n-3 series (EPA andDHA) may be increased when marine oils (fish or algae)are added to cow rations. The transfer efficiency from dietto milk, however, is low (2.6% for EPA and 4.1% for DHAin 16 groups of cows; review [21]) because of high RBHand of preferential incorporation into plasma phospholi-pids and cholesterol esters [57]. The increase in EPA andDHA concentrations in milk FA is therefore minimal whenfish oil is added to the cow ration and rarely exceeds0.5% of total FA (reviews [4, 21]). Higher transfer effi-ciencies, have been noted during the post-rumen infusionof fish oil (16–33%; review [21]) or using tuna oil-soybeanprotected from RBH by formaldehyde treatment (18–32%[151]). EPA and DHA concentrations in cow milk FA ten-ded to decrease after linseed oil supplementation, al-though milk 18:3n-3 concentration increased [29], whichconfirms that 18:3n-3 is not a significant source of milkEPA and DHA in cattle.
4.1.3 Trans FA and CLA
The diets that influence the milk t11-18:1 and CLA aremainly: (1) diets providing lipid precursors (18:2n-6 or18:3n-3) for t11-18:1 formation in the rumen and (2) dietsthat modify the microbial activity associated with PUFAhydrogenation in the rumen [27]. Combinations of thesevarious factors induce wide variations of milk CLA andtrans-18:1 concentrations, and strong interactions occurbetween forages, starchy concentrates and lipid supple-ments (see Section 5 and [114]
Vegetable oils rich in 18:2n-6 (sunflower, soybean)markedly increase milk c9t11-CLA content, up to ca. 2 g/100 g FA above controls. This effect is linear as increas-ing amounts of soybean oil (review [33]) or sunflower oil(Tab. 3) are added to the diet (up to at least 4% oil of dietDM). Adding calcium salts of rapeseed oil or soybean(which was the more efficient) to the ration increasedmilk c9t11-CLA concentration [152]. This confirms thatcalcium salts of PUFA are largely hydrogenated to transFA.
Increasing linseed oil (18:3 rich) intake from 1.5 to 3.0% ofthe diet increased milk t11-18:1 and c9t11-CLA con-
842 Y. Chilliard et al. Eur. J. Lipid Sci. Technol. 109 (2007) 828–855
centration more than linearly, almost as much as with thesame doses of sunflower oil (18:2 rich) (Tab. 3). This resultis in agreement with a trial comparing linseed and saf-flower oils [62] but differs from another where soybean oilincreased much more milk t11-18:1 and c9t11-CLA thanlinseed oil did [153]. However, it could be that in the lattertrial an unusually large amount of t11-18:1 was producedby RBH of soybean oil PUFA at the expense of 18:0,which did not increase in milk, contrary to resultsreviewed by Dewhurst et al. [23] with soybean oil.Increasing the intake of either 18:2n-6 or 18:3n-3 or both(substituted to diet c9-18:1) showed that their combinedeffect on milk c9t11-CLA (10.3 g/100 g FA) was slightlyhigher than the separate effects (10.1 for each PUFA)[154]. In sum, vegetable oils increase milk trans-18:1 andc9t11-CLA more than extruded seeds, which in turnincrease it more than raw seeds ([138, 144, 152, 155] andreview [19]).
For a given incorporation level to the ration, fish oils aremore effective at increasing the CLA concentration thanvegetable oils. Thus, c9t11-CLA proportions increasedfrom 0.2–0.6% with the control diet to 1.5–2.7% in moststudies with diets supplemented with 200–300 g/day fishoil (reviews [4, 21]). It is likely that the EPA and DHA ofthese oils, or their RBH products, indirectly but sharply
increased the t11-18:1 concentration in the rumen (Fig. 3)by inhibiting the reduction of this FA into 18:0. That wouldexplain why the combination of sunflower and fish oilstrongly increased the milk t11-18:1 and c9t11-CLA con-tent [156]. However, an extruded soybean-fish oil mixtureincreased these FA more than fish oil alone in Holstein butnot in Brown Swiss cows [157].
Besides its major effects on t11-18:1 and c9t11-CLA,plant oil supplementation modifies to some extent theprofile of other trans and conjugated isomers differentlyaccording to the oil FA profile. Thus, a high level of c9-18:1 intake in particular increases milk t61718-18:1 andt7c9-CLA [61, 99]; 18:2n-6 intake increasesmilk t61718-,t9-, t10-18:1, t12-18:1 and t10t12-, t9t11-, t8t10-, t7t9-,t10c12-, t9c11-, t8c10-, t7c9-CLA [10, 30, 59, 99]; and18:3n-3 intake increases milk c15-, t13114-, t15-, t16-18:1, c9t12-, c9t13-, t11c15-18:2, and t9t11-, t12t14-,t11t13-, c12t14-, t12c14-, t11c13-, c11t13-CLA [10, 29,30, 99] (Figs. 3, 4, 7), as well as conjugated 18:3 [144,158]. These relationships can be explained, at least inpart, by the RBH pathways from Fig. 1, combined withmammary SCD activity on trans-18:1 isomers, especiallyt7-, t12- and t13-18:1. In other respects, fish oil intakeincreases milk c11-, t61718-, t9-, t10-, t12-, t13114-18:1 and t11c15-18:2 [51, 59, 81] (Figs. 3, 4).
Fig. 7. Time-dependent changes in t11-18:1 (A), t10-18:1 (B), t11c13-CLA (C) and t9c11-CLA (D) concentra-tions (g/100 g total FA) for cows given concentrate-sunflower oil (C-S, unbroken line), maize silage-sunflower oil(M-S, broken line) or hay-linseed oil treatments (H-L, dotted line) (six animals per group). Diet compositions aredescribed in Tab. 7 (adapted from [30]).
Eur. J. Lipid Sci. Technol. 109 (2007) 828–855 Feeding factors, rumen biohydrogenation and milk fatty acids 843
4.2 Goat milk
The goat does not show any milk fat depression afteradding plant oil PUFA to high-concentrate diets [24, 25],contrary to the cow (reviews [19, 23, 34]). It is thus ofinterest to know to what extent the response to plant oilsof the milk FA profile could differ between these tworuminant species.
4.2.1 Saturated FA and oleic acid
As in cows, the potential to decrease milk medium-chainsaturated FA (10:0–16:0) in goats is very high. For exam-ple, with hay-based diets, these four FA represented 59%of goat milk fat and fell to 38% after linseed oil supple-mentation or to 33% if vitamin E was added with linseedoil [19]. The concentration of milk saturated FA that areconsidered to have the highest atherogenic potential(12:0, 14:0 and 16:0 [159]) was 43–50 g/100 g FA in milkfrom goats receiving 11 control diets and decreased to26–35 g/100 g FA in 25 lipid-supplemented diets(Tabs. 5, 6). As with cows, goat milk short-chain FA con-centrations (4:0, 6:0 and, to a lesser extent, 8:0) are eitherunchanged or only slightly reduced by dietary lipid sup-plementation or body lipid mobilization [24].
In goats, in a diet comparison combining different for-ages, concentrate percentages and lipid sources, itappears that high milk concentrations of 18:0 and c9-18:1(13–17% and 23–29 % of total FA, respectively) wereobtained either with unprotected high-oleic sunflower oil(Tab. 5) or with whole raw oilseeds, in the rank lupin. soybean . linseed . sunflower seeds . rapeseeds[19, 119, 160, 161]. Extruded soybean also increased milk18:0 and c9-18:1 [162].
However, the goat milk c9-18:1 percentage did not or onlyslightly increase after linseed or sunflower oil, or extrudedseeds, supplementation, although 18:0 was substantiallyincreased (Tabs. 5, 6). Thus, the c9-18:1 response differsbetween goat and cow. It can indeed be observed that incows the c9-18:1/18:0 ratio is not markedly decreased orincreased by sunflower, soybean or linseed oil supple-mentation (–0.06 to –0.17, Tab. 3; 10.03 [163]; 10.24[164]; 10.15 to –0.42 [30]; 10.04 to –0.29 [62]; –0.16 to–0.35 [153]; –0.06 in a meta-analysis of 17 trials, F. Glas-ser, L. Bernard, A. Ferlay, Y. Chilliard, unpublished). Ingoats, by contrast, this ratio decreased markedly in therank high-oleic sunflower oil (–0.60, n = 4 treatmentgroups) , linoleic-rich sunflower oil (–0.77, n = 4) , lin-seed oil (–0.88, n = 10) , extruded seeds (–1.09, n = 2)(Tabs. 5, 6). This suggests that the desaturation ratio of18:0 decreases more with diets that increase more theavailability of PUFA and/or trans FA (Tabs. 5, 6) for the
goat mammary gland, since these FA are putative inhibi-tors of the SCD [68, 165]. Further research is needed tounderstand if the difference between goat and cow is dueto differences in RBH or in mammary SCD regulation.Available data suggest indeed that mammary SCD couldbemore sensitive to PUFA-rich diets in goats than in cows(review [68]). Vitamin E, when added to goat linseed oil-supplemented diets, further decreased this desaturationratio while simultaneously further increasing milk trans-18:1 and 18:2 ([19] and Tab. 6). Finally, the efficiency ofhigh-oleic sunflower oil to increase milk c9-18:1 could bedue to the combination of greatly increasing 18:0 avail-ability (Tab. 5) and increasing duodenal flow of rumen-escaped c9-18:1, without increasing largely trans FAhaving inhibitory effects on mammary SCD.
The case of lupin seeds is interesting since this seed, richin c9-18:1 and 18:2n-6, is the only one which did not de-crease the 18:0 desaturation ratio and did not increase (oreven decreased) goat milk PUFA and t11-18:1 percent-ages [24], suggesting that lupin unsaturated FA weretotally hydrogenated despite being consumed as crudewhole seed.
4.2.2 Polyunsaturated FA
4.2.2.1 Linoleic acid
In the absence of supplementary lipids, the proportion of18:2n-6 in goat milk FA is between 2 and 3%. Whenrations are supplemented with 18:2n-6-rich seeds or oilslike soybean or sunflower, that proportion rarely exceedscontrol values by more than 1.5% ([160, 162] andTabs. 5, 6). Comparing the effects of sunflower oil andseeds in goats revealed that seed 18:2n-6 was, para-doxically, more strongly hydrogenated to 18:0 than oil18:2n-6, the latter being more recovered either intact or inthe form of t11-18:1 and c9t11-CLA in milk [24]. It maytherefore be supposed that the release of seed lipids wasslow, which enhanced their total hydrogenation. A similarobservation was made with 18:2n-6-rich lupin seed,which strongly increased milk 18:0 and c9-18:1 while re-ducing 18:2n-6 and c9t11-CLA. This may explain why rawoilseeds are more efficient at increasing milk 18:0 and c9-18:1 than free oils (see Section 4.2.1).
The addition of linseed oil to goat’s diet decreased themilk 18:2n-6 percentage while it increased the 18:3n-3percentage. Opposite responses between these twoPUFA were also observed when sunflower oil (18:2n-6rich) was added (Tab. 5). Besides illustrating that the dif-ferent PUFA are not secreted independently from eachother, it should be noted that such a substitution seems tobe less marked in cows (Tab. 3) than in goats.
844 Y. Chilliard et al. Eur. J. Lipid Sci. Technol. 109 (2007) 828–855
4.2.2.2 Linolenic acid and long-chain n-3 FA
Few trials have been conducted where goats’ diets weresupplemented with linseed oil or seeds. The milk 18:3n-3response suggests that 18:3n-3 from whole crude lin-seeds was more widely hydrogenated to 18:0 than 18:3n-3 from free oil [24], similar to what was described abovefor sunflower 18:2n-6. The response to extruded linseeds(13.6% oil in hay-based diet DM) was high in the goat,where 18:3n-3 increased more (11.9 g/100 g FA) thanafter linseed oil supplementation (10.9 g/100 g FA)(Tab. 6). The response to extruded linseed fat-rich cake(equivalent to 1.5% oil addition to a “dry totally mixed”diet) was, however, not so high (10.5 g/100 g FA) [166].Formaldehyde treatment of whole linseed increased thegoat milk 18:3n-3 concentration more than untreatedseed (11.1 vs. 10.6 g/100 g FA), but not beyond theeffect of a corresponding dose of unprotected oil (11.3)[24, 165]. The goat milk 18:3n-3/18:2n-6 ratio was sharplyincreased by linseed oil (130 g/day) and, more markedly,by extruded linseed supplementation (Tabs. 5, 6). Alto-gether, the milk 18:3n-3 concentration responded more totreated or untreated linseeds or linseed oil supplementa-tion in the goat than in the cow (review [19], Tabs. 3, 5, 6and Section 4.1.2.2). This could be related to the fact thatthe 18:3n-3 milk/plasma ratio in the goat was twice that inthe cow and that the correlation between milk and plasma18:3n-3 was much higher in the goat (Tab. 1).
There are few studies in goats concerning the effects ofdietary marine oils in order to increase milk EPA and DHA.The transfer efficiency from diet to milk was low (4–5%)for these two FA from non-protected oils because of highRBH and was increased to some extent with protectedoils [167, 168].
4.2.3 Trans FA and CLA
The dietary factors that influence the milk t11-18:1 andCLA concentration are basically the same in goats andcows. There is a strong linear correlation between milkc9t11-CLA and t11-18:1 concentrations among a widevariety of diets in goats (slope = 0.40 [24]) as in cows(slope 0.38–0.43 [60–62]). However, in 36 diets studied ingoats (Tabs. 5, 6), the c9t11-CLA/t11-18:1 ratio was 0.6–0.7 for control diets compared to 0.3–0.5 for lipid-sup-plemented diets. With combinations of five different for-ages with either no oil addition or c9-18:1-, 18:2n-6- or18:3n-3-rich oils, a considerable range of c9t11-CLA wasobserved: from 0.3 to 5.1% of total FA. The main factor ofvariation was the nature of oil, with sunflower (18:2n-6rich)� linseed (18:3n-3 rich).. high-oleic sunflower (c9-18:1 rich) . no oil addition. The response to c9-18:1-richoil, albeit much less than a similar amount of PUFA-rich
oils, is consistent with a possible c9-18:1 isomerizationinto t11-18:1 in the rumen [47] or could be due to an inhi-bition of the last step in hydrogenation of dietary PUFA.The responses were lower with extruded linseeds or sun-flower seeds than with the same doses of oils (Tab. 6).
Few data are available on the influence of feeding plantoils on the various 18:1 and 18:2 isomers in goat milk.c9t11-CLA is the most important CLA isomer and itsconcentration is the most variable because of the impor-tance of its mammary synthesis by SCD. In addition, thisenzyme probably synthesizes t7c9-CLA [66]. This isomeris not well separated in studies using only GLC for ana-lyzing the milk FA profile; preliminary results suggest,however, that it is increased in goats fed high-oleic sun-flower oil [169], in agreement with data regarding cows(see Section 4.1.3). Linseed oil increases goat milk c9c11-and/or t11c13-CLA as well as c9t13-18:2 and t11c15-18:2 [19], whereas t10c12-CLA generally remains at tracelevels in goats [25, 119].
5 Effects of forage-concentrate-lipidinteractions on milk FA and persistency ofthe responses
The changes in milk FA composition that are obtained bylipid supplementation of ruminant diets are linked to thelipid source (animal fat, plant or marine oil), and to theirpresentation form, technological treatment and amountincluded in the diet (see Section 4). However, theresponses are also largely dependent on both the foragesource and the diet forage/concentrate ratio (reviews [19,23]).
5.1 Cow milk
Linseed oil supplementation interacts significantly withthe diet forage/concentrate ratio on the milk concentra-tion of several FA: The oil effect was higher on t10-18:1,t11c15-18:2 and 18:3n-3 when added to a high-con-centrate diet, and was higher on 18:0 and c9-18:1(increases) and 16:0 (decrease) when added to a high-forage diet [29]. Although factorial interaction was notstudied, changing concentrate percentage and soybeanoil intake together strongly increased milk fat con-centrations of t10-18:1, t7c9- and t10c12-CLA, mainlyat the expense of 4:0–16:0, t11-18:1, t13114-18:1 andc9t11-CLA [75]. Indirect comparison suggests that sun-flower oil could be more efficient than soybean oil toincrease milk t10-18:1 when added to similar high-con-centrate diets [30, 75], whereas direct comparisonshowed that linseed oil is less efficient than sunfloweroil is ([59] and Fig. 3).
Eur. J. Lipid Sci. Technol. 109 (2007) 828–855 Feeding factors, rumen biohydrogenation and milk fatty acids 845
In a study on linseed and sunflower oils (Tab. 3), milk18:0 and c9-18:1 concentrations increased even morewhen adding plant oils to a grass silage compared to amaize silage diet (13.4 vs. 1.9 and 4.7 vs. 2.8 g/100 gFA, respectively) whereas the opposite was true forc9t11-CLA (10.7 vs. 11.3 g/100 g FA, respectively),t10111-18:1 and PUFA (e.g. 10.3 vs. 10.45 g/100 g FA,respectively, for the 18:2n-6 response to sunflower oil)(Tab. 3). Thus, RBH seems to be less complete withmaize silage, likely due either to a lower ruminal pH orchanges in microbial population with this diet. Further-more, there was a greater decrease in milk fat contentwhen oils were added to a maize than a grass silage-based diet (Tab. 3), in agreement with previous obser-vations on maize silage diets supplemented either withsoybean or rapeseeds, which decreased the milk 4:0–16:0 yield without changing total 18:1 [137], or with tal-low, which decreased cell wall (NDF) digestion [170] andmilk fat content [171] and increased milk t10-18:1 con-centration [132].
The effect of the forage source was also observed withfish1 sunflower oil-supplemented diets: Replacing grasssilage with maize silage increased 12:0, 14:0, t10-18:1,t9c11-CLA, EPA and DHA and decreased 18:0, c9-18:1,t15-18:1, t16-18:1, trans-18:2 and 18:3n-3, whileincreasing the concentrate level increased milk t10-18:1,t9c11- and t10c12-CLA, 18:2n-6, EPA, DHA anddecreased c9t11-CLA, other CLA having a trans-11 dou-ble bond and 18:3n-3, with few interactions with the for-age source [78]. In cows receiving oil-rich rapeseed cake,replacing grass silage with maize silage decreased milkfat content, increased milk fat concentrations of c9-18:1,t10-18:1 (14.0 g/100 g FA), c9t11- and t10c12-CLA,18:2n-6 and decreased 4:0–16:0, 18:0, 18:3n-3, and theeffects were more marked for t10-18:1 and t10c12-CLAwhen the dietary concentrate and/or starch percentagewas higher [71]. Again, RBH seems to be less completewith maize silage.
In most of the studies reported above, a common featureis an increase in milk t10-18:1 with either high-con-centrate or maize silage diets supplemented with PUFA-rich oils. In studies reviewed by Bauman and Griinari([34]) and Shingfield and Griinari (this issue), low-fiber,high-starch diets supplemented with PUFA-rich plant oilsharply reduce mammary lipid secretion and stronglyincrease the proportions of milk t10-18:1 and, to a cer-tain extent, of t10c12-CLA. It is therefore possible thatt10c12-CLA results from RBH modifications induced bylow-fiber diets and is one of the precursors of the t10-18:1 yield in the rumen. It is worth noting that, undersuch conditions, milk t11-18:1 and c9t11-CLA synthesesonly increased slightly (trans-11 to trans-10 shift) by
comparison with what happened with high-fiber dietssupplemented with oil (when t11-18:1 is the major inter-mediate of PUFA RBH) [114].
Furthermore, it was recently observed that the milk FAresponse to plant and/or marine oil supplementation istime dependent (Tab. 7), probably reflecting RBH and/ormetabolic adaptations. Bauman et al. [172] and Dhimanet al. [173], with respect to maize silage-containing diets,first reported that the milk c9t11-CLA response could betransient, peaking during the second week after begin-ning lipid supplementation. It was subsequently observedthat the c9t11-CLA response to lipid supplementationwas higher with a diet containing 60% hay than 70%maize silage, and that its decrease after 3 wk of supple-mentation was accompanied by an increase in the milk fatt10-18:1 percentage, which was more marked with maizesilage, whatever the source of plant or marine oil ([174]and Tab. 7). The maximum c9t11-CLA transient responsewas observed at 2–3 wk after beginning lipid supple-mentation in studies using mixed diets containing 25%maize silage and 50% concentrates [157, 175], but at 5–6 days with diets higher in maize silage and/or con-centrates ([30, 31], Tab. 7, Fig. 7). With the addition of oilto diets rich in maize silage and/or concentrates, a largedecrease in milk fat content and increase in milk fat t10-18:1 percentage (up to 4.5–18.6 g/100 g FA) wereobserved concurrent with the c9t11-CLA decrease [30,31, 174] as well as increases in milk-specific trans FA,including t61718-18:1, t10c12- and t9c11-CLA [30, 31].
By contrast, when diets were based on grass silage [176],hay [30], or legume silage and hay [62], the milk fat c9t11-CLA response to oil supplements was stable at a mediumlevel for 14 wk [176], at a high level for at least 3 wk ([30],Fig. 7) or at a very high level for at least 8 wk ([62], Tab. 7).At the same time, t10-18:1 remained lower than 0.7 [30] or1.4 g/100 g FA [62].
Adding dietary vitamin E has been shown to avoid thetrans-11 to trans-10 shift in cows receiving a maize silage-based diet supplemented with extruded linseeds and lin-seed oil; however, this effect was observed only if vita-min E was added at the start of linseed supplementationbut not if it was added once the trans-11 to trans-10 shifthad occurred [177]. No significant effect of vitamin Eaddition on milk t10-18:1 concentration was observed incows receiving a legume silage- and hay-based dietsupplemented with safflower oil; however, a trend toincrease t10-18:1 was observed in the absence of mon-ensin, whereas the stimulatory effect of monensin on milkt10-18:1 was abolished by vitamin E [62]. The addition ofmonensin together with a high level of safflower oil (6% ofthe diet) maximized the milk c9t11-CLA concentration(5.1 g/100 g FA) due to the simultaneous increases in both
{AH, GH = alfalfa or grass hay; AS, BS, GS, MS = alfalfa, barley, grass or maize silage (respectively). The figures indicatepercentages in diet DM.{Concentrate percentage in diet DM.§ ESB, FM, FO, LO, RO, SFO, SO = extruded soybean, fish meal, fish oil, linseed oil, rapeseed oil, safflower oil, sunflower oil(respectively). The figures indicate percentages of related oils in diet DM.nr = not reported.
t11-18:1 and t10-18:1 [62]. The effect of monensin in cul-tures of ruminal microorganisms was to increase t10-18:1formation, interacting with PUFA addition and grainsource [178].
After adding linseed oil to a hay-based diet, milk 18:3n-3increased slightly until day 6 and then returned to thebaseline at day 9 ([30] and unpublished data). This sug-gests that, although there was no trans-11 to trans-10
Eur. J. Lipid Sci. Technol. 109 (2007) 828–855 Feeding factors, rumen biohydrogenation and milk fatty acids 847
shift under these conditions (see above), the rumenmicroflora needed a few days before adapting to PUFA-rich oil feeding. Furthermore, adding fish oil and sun-flower oil to a maize silage-based diet increased milkEPA and DHA to a maximum at 5 days, after which theapparent transfer efficiency from diet to milk decreasedfrom ca. 5% to less than 1.5% [31], thus suggesting thattime-dependent adaptation in RBH of long-chain n-3 FAalso occurred with diets favoring the trans-11 to trans-10shift.
5.2 Goat milk
Forage-concentrate-lipid interactions also occur in goats.Thus, dietary linseedoil increasedmoremilk 18:3n-3whengiven to goats receiving hay-based diets than diets eitherrich in concentrates (Tab. 6, trials E and F) or based onmaize silage (Tab. 5, trial A). This interaction is the oppo-site of what was observed in cows (Tab. 3) and deservesfurther research. Furthermore, the milk c9-18:1 responseto high-oleic sunflower oil supplementation was higherwith hay- than with maize silage-based diet, whereas the18:0 responsewas lower (Tab. 5, trial A), in agreementwiththe hypothesis that diets increasing the yield of trans FAcould inhibit mammary SCD (see Section 4.2.1).
For a given oil supplementation, the response of c9t11-CLA to oil strongly interacts with forage source. Thus, theresponse to sunflower oil was highest with maize silage(trial D vs. trial C) and lowest with high-concentrate diet(68%, trial F), whereas the response to linseed oil waslower with maize silage than with either hay or fresh grass(Tabs. 5, 6). While the milk c9t11-CLA response to linseed
Fig. 8. Persistency of goat milk c9t11-CLA response afterlipid supplementation to high- or low-forage diets(adapted from [25, 185]).
oil supplementation did not change when the dietaryconcentrate increased from 30 to 54%, either in thepresence or absence of vitamin E supplementation, itdecreased with a high-concentrate (69%) diet (Tab. 6,trials E and F). This suggests that a minimal range of 55–65% concentrate in the diet is needed to decrease themilk c9t11-CLA response to plant oils, and that the bestresponses are allowed by association of sunflower oil witheither maize silage-based (Tab. 5, trial D) or hay-rich diets(Fig. 8).
Tab. 8. Mid-term effects{ of different diets and/or supplements on milk FA composition (g/100 g total FA) in dairy cows andgoats (see text for the origin of data).
Diets/supplements Pasture High concentrate 18:2-rich oil Linseed oil High concentrate1 plant oil
{Effects after at least 3 wk on the diet, compared to a winter medium-concentrate diet, based on grass hay or silage.{ Isomers of 18:1 and 18:2 (conjugated and non-conjugated).1, –, 0 = increase, decrease, no change, respectively; (. . .)* indicates an effect in goat that differs from the effect in cow.
848 Y. Chilliard et al. Eur. J. Lipid Sci. Technol. 109 (2007) 828–855
Data in cows showed that milk t11-18:1 and c9t11-CLAresponses to lipid supplementation are transient withsome diets (see Section 5.1). Such is not the case ingoats: even with high-concentrate diets supplementedwith PUFA-rich oils, the response of c9t11-CLA wasmaximal 2 wk after the beginning of oil supplementationand then remained stable at very high levels (Fig. 8) de-spite the t10-18:1 percentage increasing 5–8 times abovecontrol values in diets without dietary oils (Tab. 6). Fur-thermore, adding sunflower oil and fish oil to goat dietincreasedmilk c9t11-CLA up to 10 g/100 g FA, i.e. amongthe highest values ever recorded in ruminant milk [179].Finally, high milk CLA levels were observed after 9–10 wkof lipid supplementation, without a decrease from whatwas observed in the same goats after 5 wk (Fig. 9). Thisconfirms that the goat is a very good responder and thatits milk c9t11-CLA response is stable for at least2.5 months. This stability may also be related to the sta-bility of t10-18:1, which always remained at levels,3.5 g/100 g FA (Tabs. 5, 6), much lower than those reported incows receiving similar diets (see Section 5.1), thus con-tributing to the lack of milk fat depression in goatsreceiving high-concentrate diets with PUFA-rich oils (seeSection 2.3). A very stable response was also observedfor other milk FA, including 18:3n-3 (Fig. 9), which couldbe related to the good response of the goat for this PUFA(see Section 4.1.2.2).
It should be stressed, however, that the achievement ofhigh levels of goat milk c9t11-CLA (.2% of total FA) withoil supplements is accompanied by high levels not only oft11-18:1 (6–13%) but also of other trans isomers of 18:1and conjugated or non-conjugated 18:2 (3–6% withgrass-based diets, 9–11%with maize silage diets and, fora given forage, linseed oil . high-oleic sunflower oil. sunflower oil; Tabs. 5, 6).
6 Conclusion
There is a considerable potential to modify milk FA com-position by changing cow or goat feeding conditions(Tab. 8). RBH, combined with mammary lipogenic andD-9 desa-turation pathways, considerably modifies theprofile of dietary FA and thus milk composition. Pasturehas major effects to decrease saturated FA and increaseseveral FA considered as favorable for human health (c9-18:1, 18:3n-3 and c9t11-CLA), compared to winter diets,especially those based onmaize silage and concentrates.Large variations are, however, putatively linked to grassvegetation stage and/or quality, deserving further re-search. Plant lipid supplements, especially linseed, haveeffects similar to pasture although they simultaneously toa larger extent, increase several trans isomers of 18:1 and
Fig. 9. Persistency of goat milk c9t11-CLA, t10-18:1 and18:3n-3 responses to lipid supplementation (adaptedfrom [19, 25, 182]). Twenty groups of 10–12 goatsreceived either a control diet (s), or a lipid-supplementeddiet [linseed oil (u); oleic sunflower oil (D)] for either 9(trial E in Tab. 6) or 10 wk (trials A and B in Tab. 5). Allslopes were significantly different from 1.0 (p ,0.05) andintercepts did not differ from zero (p .0.20).
conjugated or non-conjugated 18:2, especially whenadded to maize silage or concentrate-rich diets. The goatseems to respond better for milk 18:3n-3 and c9t11-CLA,sometimes less for c9-18:1, and to be less prone to theRBH trans-11 to trans-10 shift, which has been shown tobe time-dependent in the cow. Further research is neededto better manage RBH and favor the mammary secretionof either 18:0 1 c9-18:1 or t11-18:1 1 c9t11-CLA. Therespective physiological roles of most milk trans FA havenot been studied to date. However, encouraging results
Eur. J. Lipid Sci. Technol. 109 (2007) 828–855 Feeding factors, rumen biohydrogenation and milk fatty acids 849
came recently from animal [8, 9] or human studies [10,180] using dairy products modified by changing ruminantnutrition, which need confirmation, together with theevaluation of effects on dairy product sensorial quality,before recommending a larger use of lipid supplementsand how to combine them with the different feeding sys-tems used by dairy farmers.
Acknowledgments
The authors thank P. B�raud and C. Delavaud for assis-tance during the preparation of the manuscript, as well asA. Roy, C. Leroux and K. Shingfield for helpful discus-sions. Experimental work was funded by the Poitou-Charentes Region, the French Ministry of Research (AQS-P204 and AQS-P504), the INRA Program “Micronutrientsin animal products”, the BIOCLA Project QLK1-2002-02362 within the EU Fifth Framework Research program(www.teagasc.ie/research/dprc/biocla/index.htm) andthe LIPGENE Project within the EU funded Sixth Frame-work Research program (www.lipgene.tcd.ie).
References
[1] C. M. Williams: Dietary fatty acids and human health. AnnZootech. 2000, 49, 165–180.
[2] R. G. Jensen: The composition of bovine milk lipids: January1995 to December 2000. J Dairy Sci. 2002, 85, 295–350.
[3] P. W. Parodi: Milk fat in human nutrition. Aust J Dairy Tech-nol. 2004, 59, 3–59.
[4] D. I. Givens, K. J. Shingfield: Optimizing dairy milk fatty acidcomposition. In: Improving the Fat Content of Foods. Eds. C.Williams, J. Buttriss, Woodhead Publishing Limited, Cam-bridge (UK) 2006, pp. 252–280.
[5] R. H. Knopp, B. M. Retzlaff: Saturated fat prevents coronaryartery disease? An American paradox. Am J Clin Nutr. 2004,80, 1102–1103.
[6] H. Dabadie, E. Peuchant, M. Bernard, P. LeRuyet, F. Mendy:Moderate intake of myristic acid in sn-2 position has bene-ficial lipidic effects and enhances DHA of cholesteryl estersin an interventional study. J Nutr Biochem. 2005, 16, 375–382.
[7] P. L. Zock: Health problems associated with saturated andtrans fatty acids intake. In: Improving the Fat Content ofFoods. Eds. C. Williams, J. Buttriss, Woodhead PublishingLimited, Cambridge (UK) 2006, pp. 3–24.
[8] A. L. Lock, P. W. Parodi, D. E. Bauman: The biology of transfatty acids: Implications for human health and the dairyindustry. Aust J Dairy Technol. 2005, 60, 134–142.
[9] A. Roy, J. M. Chardigny, D. Bauchart, A. Ferlay, S. Lorenz, D.Durand, D. Gruffat, Y. Faulconnier, J. L. S�b�dio, Y. Chilliard:Butters rich either in trans-10-C18:1 or in trans-11-C18:1plus cis-9, trans-11 CLA differentially affect plasma lipidsand aortic fatty streak in experimental atherosclerosis inrabbits. Animal. 2007, 1, 467–476.
[10] K. J. Shingfield, Y. Chilliard, V. Toivonen, P. Kairenuis, I.Givens: Trans fatty acids and bioactive lipids in ruminantmilk. Adv Exp Med Biol. 2007, in press.
[11] E. Warensjo, J. H. Jansson, L. Berglund, K. Boman, B.Ahren, L. Weinehall, B. Lindahl, G. Hallmans, B. Vessby:Estimated intake of milk fat is negatively associated withcardiovascular risk factors and does not increase the risk ofa first acute myocardial infarction. A prospective case-con-trol study. Br J Nutr. 2004, 91, 635–642.
[12] S. Wongtangtintharn, H. Oku, H. Iwasaki, T. Toda: Effect ofbranched-chain fatty acids on fatty acid biosynthesis of hu-man breast cancer cells. J Nutr Sci Vitaminol. 2004, 50, 137–143.
[13] J. Lopez-Miranda, P. P�rez-Martinez, F. P�rez-Jim�nez:Health benefits of monounsaturated fatty acids. In: Improv-ing the Fat Content of Foods. Eds. C. Williams, J. Buttriss,Woodhead Publishing Limited, Cambridge (UK) 2006, pp.71–106.
[14] A. M. Minihane, J. A. Lovegrove: Health benefits of poly-unsaturated fatty acids (PUFAs). In: Improving the Fat Con-tent of Foods. Eds. C. Williams, J. Buttriss, Woodhead Pub-lishing Limited, Cambridge (UK) 2006, pp. 107–140.
[15] S. Banni, G. Carta, E. Angioni, E. Murru, P. Scanu, M. P.Melis, D. E. Bauman, S. M. Fischer, C. Ip: Distribution ofconjugated linoleic acid and metabolites in different lipidfractions in the rat liver. J Lipid Res. 2001, 42, 1056–1061.
[16] P. Yaqoob, S. Tricon, G. C. Burdge, P. C. Calder: Conjugatedlinoleic acids (CLAs) and health. In: Improving the Fat Con-tent of Foods. Eds. C. Williams, J. Buttriss, Woodhead Pub-lishing Limited, Cambridge (UK) 2006, pp. 182–212.
[17] A. De la Torre, E. Debiton, D. Durand, J. M. Chardigny, O.Berdeaux, O. Loreau, C. Barthomeuf, D. Bauchart, D. Gruf-fat: Conjugated linoleic acid isomers and their conjugatedderivatives inhibit growth of human cancer cell lines. Anti-cancer Res. 2005, 25, 3943–3949.
[18] D. L. Palmquist, A. D. Beaulieu, D. M. Barbano: Feed andanimal factors influencing milk fat composition. J Dairy Sci.1993, 76, 1753–1771.
[19] Y. Chilliard, A. Ferlay: Dietary lipids and forages interactionson cow and goat milk fatty acid composition and sensoryproperties. Reprod Nutr Dev. 2004, 44, 467–492.
[20] Y. Chilliard, G. Gagliostro, J. Flechet, J. Lefaivre, I. Sebas-tian: Duodenal rapeseed oil infusion in early and midlacta-tion cows. 5. Milk fatty acids and adipose tissue lipogenicactivities. J Dairy Sci. 1991, 74, 1844–1854.
[21] Y. Chilliard, A. Ferlay, M. Doreau: Effect of different types offorages, animal fat or marine oils in cow’s diet on milk fatsecretion and composition, especially conjugated linoleicacid (CLA) and polyunsaturated fatty acids. Livest Prod Sci.2001, 70, 31–48.
[22] A. L. Lock, K. J. Shingfield: Optimising milk composition. In:Dairying – Using Science to Meet Consumers’s Needs. Eds.E. Kebreab, J. Mills, D. E. Beever, Occasional PublicationNo 29 of the British Society of Animal Science NottinghamUniversity Press, Lougborough (UK) 2004, pp. 107–108.
[23] R. J. Dewhurst, K. J. Shingfield, M. R. F. Lee, N. D. Scollan:Increasing the concentrations of beneficial polyunsaturatedfatty acids in milk produced by dairy cows in high-foragesystems. Anim Feed Sci Technol. 2006, 131, 168–206.
[24] Y. Chilliard, A. Ferlay, J. Rouel, G. Lamberet: A review ofnutritional and physiological factors affecting goat milk lipidsynthesis and lipolysis. J Dairy Sci. 2003, 86, 1751–1770.
[25] Y. Chilliard, J. Rouel, A. Ferlay, L. Bernard, P. Gaborit, K.Raynal-Ljutovac, A. Lauret, C. Leroux: Optimising goat’smilk and cheese fatty acid composition. In: Improving theFat Content of Foods. Eds. C. Williams, J. Buttriss, Wood-head Publishing Limited, Cambridge (UK) 2006, pp. 281–312.
[26] C. G. Harfoot, G. P. Hazlewood: Lipid metabolism in therumen. In: The Rumen Microbial Ecosystem. Eds. P. N.
850 Y. Chilliard et al. Eur. J. Lipid Sci. Technol. 109 (2007) 828–855
Hobson, C. S. Stewart, Blackie Academic & Professional,London (UK) 1997, pp. 382–426.
[27] D. L. Palmquist, A. L. Lock, K. J. Shingfield, D. E. Bauman:Biosynthesis of conjugated linoleic acid in ruminants andhumans. Adv Food Nutr Res. 2005, 50, 179–217.
[28] J. Kraft, M. Collomb, P. Mockel, R. Sieber, G. Jahreis: Dif-ferences in CLA isomer distribution of cow’s milk lipids.Lipids. 2003, 38, 657–664.
[29] J. J. Loor, A. Ferlay, A. Ollier, M. Doreau, Y. Chilliard: Rela-tionship among trans and conjugated fatty acids and bovinemilk fat yield due to dietary concentrate and linseed oil. JDairy Sci. 2005, 88, 726–740.
[30] A. Roy, A. Ferlay, K. J. Shingfield, Y. Chilliard: Examination ofthe persistency of milk fatty acid composition responses toplant oils in cows given different basal diets, with particularemphasis on trans-C18:1 fatty acids and isomers of con-jugated linoleic acid. Anim Sci. 2006, 82, 479–492.
[31] K. J. Shingfield, C. K. Reynolds, G. Hervas, J. M. Griinari, A.S. Grandison, D. E. Beever: Examination of the persistencyof milk fatty acid composition responses to fish oil and sun-flower oil in the diet of dairy cows. J Dairy Sci. 2006, 89, 714–732.
[32] J. M. Griinari, D. E. Bauman: Milk fat depression: Concepts,mechanisms and management applications. In: RuminantPhysiology: Digestion, Metabolism and Impact of Nutritionon Gene Expression, Immunology and Stress. Eds. K. Sejr-sen, T. Hvelplund, M. O. Nielsen, Wageningen AcademicPublishers, Wageningen (The Netherlands) 2006, pp. 389–417.
[33] Y. Chilliard, A. Ferlay, R. M. Mansbridge, M. Doreau: Rumi-nant milk fat plasticity: Nutritional control of saturated,polyunsaturated, transand conjugated fatty acids. AnnZootech. 2000, 49, 181–205.
[34] D. E. Bauman, J. M. Griinari: Nutritional regulation of milk fatsynthesis. Annu Rev Nutr. 2003, 23, 203–227.
[35] M. Doreau, A. Ferlay: Digestion and utilisation of fatty acidsby ruminants. Anim Feed Sci Technol. 1994, 45, 379–396.
[36] T. C. Jenkins: Protection of fatty acids against ruminal bio-hydrogenation. In: 4th Euro Fed Lipid Congress “Oils, Fatsand Lipids for a Healthier Future”. Euro Fed Lipid, Frankfurt(Germany) 2006, p. 554.
[37] M. Doreau, D. I. Demeyer, C. J. Van Nevel: Transformationsand effects of unsaturated fatty acids in the rumen. Con-sequences on milk fat secretion. In: Milk Composition, Pro-duction and Biotechnology. Eds. R. A. S. Welch, D. J. W.Burns, S. R. Davis, A. I. Popay, C. G. Prosser, CAB Interna-tional, Oxford (UK) 1997, pp. 35–72.
[38] K. F. Kalscheur, B. B. Teter, L. S. Piperova, R. A. Erdman:Effect of dietary forage concentration and buffer addition onduodenal flow of trans-C18:1 fatty acids and milk fat pro-duction in dairy cows. J Dairy Sci. 1997, 80, 2104–2114.
[39] J. J. Loor, K. Ueda, A. Ferlay, Y. Chilliard, M. Doreau: Biohy-drogenation, duodenal flow, and intestinal digestibility oftrans fatty acids and conjugated linoleic acids in response todietary forage:concentrate ratio and linseed oil in dairycows. J Dairy Sci. 2004, 87, 2472–2485.
[40] C. J. Van Nevel, D. I. Demeyer: Influence of pH on lipolysisand biohydrogenation of soybean oil by rumen contents invitro. Reprod Nutr Dev. 1996, 36, 53–63.
[41] A. Troegeler-Meynadier, L. Bret-Bennis, F. Enjalbert: Ratesand efficiencies of reactions of ruminal biohydrogenation oflinoleic acid according to pH and polyunsaturated fattyacids concentrations. Reprod Nutr Dev. 2006, 46, 713–724.
[42] M. Keeney: Lipid metabolism in the rumen. In: Physiology ofDigestion and Metabolism in the Ruminant. Ed. A. T. Phillip-son, Oriel Press, Newcastle upon Tyne (UK) 1970, pp. 489–503.
[43] J. J. Loor, K. Ueda, A. Ferlay, Y. Chilliard, M. Doreau: Intest-inal flow and digestibility of trans fatty acids and conjugatedlinoleic acids (CLA) in dairy cows fed a high-concentrate dietsupplemented with fish oil, linseed oil, or sunflower oil. AnimFeed Sci Technol. 2005, 119, 203–225.
[44] F. Akraim, M. C. Nicot, P. Weill, F. Enjalbert: Effects of pre-conditioning and extrusion of linseed on the ruminal biohy-drogenation of fatty acids. 1. In vivo studies. Anim Res.2006, 55, 83–91.
[45] T. Hino, S. Fukuda: Biohydrogenation of linoleic and linolenicacids, and production of their conjugated isomers by Butyr-ivibrio fibrisolvens. In: 4th Euro Fed Lipid Congress “Oils,Fats and Lipids for a Healthier Future”. Euro Fed Lipid,Frankfurt (Germany) 2006, p 551.
[46] J. P. Jouany, B. Lassalas, M. Doreau, F. Glasser: Dynamicfeatures of the rumen metabolism of linoleic acid, linolenicacid, and linseed oil measured in vitro. Lipids. 2007, in press.
[47] E. E. Mosley, G. L. Powell, M. B. Riley, T. C. Jenkins: Micro-bial biohydrogenation of oleic acid to trans isomers in vitro. JLipid Res. 2002, 43, 290–296.
[48] J. M. Proell, E. E. Mosley, G. L. Powell, T. C. Jenkins: Iso-merization of stable isotopically labeled elaidic acid to cisand transmonoenes by ruminal microbes. J Lipid Res. 2002,43, 2072–2076.
[49] L. S. Piperova, J. Sampugna, B. B. Teter, K. F. Kalscheur, M.P. Yurawecz, Y. Ku, K. M. Morehouse, R. A. Erdman: Duo-denal and milk trans octadecenoic acid and conjugatedlinoleic acid (CLA) isomers indicate that postabsorptivesynthesis is the predominant source of cis-9-containing CLAin lactating dairy cows. J Nutr. 2002, 132, 1235–1241.
[50] M. Doreau, Y. Chilliard: Effects of ruminal or postruminal fishoil supplementation on intake and digestion in dairy cows.Reprod Nutr Dev. 1997, 37, 113–124.
[51] K. J. Shingfield, S. Ahvenjarvi, V. Toivonen, A. �r�l�, K. V.Nurmela, P. Huhtanen, J. M. Griinari: Effect of dietary fish oilon biohydrogenation of fatty acids and milk fatty acid con-tent in cows. Anim Sci. 2003, 77, 165–179.
[52] A. A. AbuGhazaleh, T. C. Jenkins: Disappearance of doc-osahexaenoic and eicosapentaenoic acids from cultures ofmixed ruminal microorganisms. J Dairy Sci. 2004, 87, 645–651.
[53] T. T. Chow, V. Fievez, A. P. Moloney, K. Raes, D. Demeyer, S.De Smet: Effect of fish oil on in vitro rumen lipolysis, appar-ent biohydrogenation of linoleic and linolenic acid andaccumulation of biohydrogenation intermediates. AnimFeed Sci Technol. 2004, 117, 1–12.
[54] R. Bickerstaffe, D. E. Noakes, E. F. Annison: Quantitativeaspects of fatty acid biohydrogenation, absorption andtransfer into milk fat in the lactating goat, with special refer-ence to the cis- and trans-isomers of octadecenoate andlinoleate. Biochem J. 1972, 130, 607–617.
[55] F. Glasser, M. Doreau, A. Ferlay, J. J. Loor, Y. Chilliard: Milkfatty acids: Mammary synthesis could limit transfer fromduodenum in cows. Eur J Lipid Sci Technol. 2007.
[56] F. Enjalbert, M. C. Nicot, C. Bayourthe, R. Moncoulon: Duo-denal infusions of palmitic, stearic or oleic acids differentlyaffect mammary gland metabolism of fatty acids in lactatingdairy cows. J Nutr. 1998, 128, 1525–1532.
[57] S. M. Kitessa, S. K. Gulati, J. R. Ashes, E. Fleck, T. W. Scott,P. D. Nichols: Utilisation of fish oil in ruminants. I. Fish oilmetabolism in sheep. Anim Feed Sci Technol. 2001, 89,189–199.
[58] G. Gagliostro, Y. Chilliard, M. J. Davicco: Duodenal rape-seed oil infusion in early and midlactation cows. 3. Plasmahormones and mammary apparent uptake of metabolites. JDairy Sci. 1991, 74, 1893–903.
Eur. J. Lipid Sci. Technol. 109 (2007) 828–855 Feeding factors, rumen biohydrogenation and milk fatty acids 851
[59] J. J. Loor, A. Ferlay, A. Ollier, K. Ueda, M. Doreau, Y. Chil-liard: High-concentrate diets and polyunsaturated oils altertrans and conjugated isomers in bovine rumen, blood, andmilk. J Dairy Sci. 2005, 88, 3986–3999.
[60] J. M. Griinari, D. E. Bauman: Biosynthesis of conjugatedlinoleic acid and its incorporation into meat and milk inruminants. In: Advances in Conjugated Linoleic Acid Re-search. Eds. M. P. Yurawecz, M. M. Mossoba, J. K. G. Kra-mer, M. W. Pariza, G. J. Nelson, AOCS Press, Champaign, IL(USA) 1999, pp. 180–200.
[61] P. Secchiari, M. Antongiovanni, M. Mele, A. Serra, A. Buc-cioni, G. Ferruzzi, F. Paoletti, F. Petacchi: Effect of kind ofdietary fat on the quality of milk fat from Italian Friesiancows. Livest Prod Sci. 2003, 83, 43–52.
[62] J. A. Bell, J. M. Griinari, J. J. Kennelly: Effect of safflower oil,flaxseed oil, monensin, and vitamin E on concentration ofconjugated linoleic acid in bovine milk fat. J Dairy Sci. 2006,89, 733–748.
[63] M. C. Barber, R. A. Clegg, M. T. Travers, R. G. Vernon: Lipidmetabolism in the lactating mammary gland. Biochim Bio-phys Acta. 1997, 1347, 101–126.
[64] B. A. Corl, L. H. Baumgard, D. A. Dwyer, J. M. Griinari, B. S.Phillips, D. E. Bauman: The role of delta(9)-desaturase in theproduction of cis-9, trans-11 CLA. J Nutr Biochem. 2001, 12,622–630.
[65] J. M. Griinari, B. A. Corl, S. H. Lacy, P. Y. Chouinard, K. V.Nurmela, D. E. Bauman: Conjugated linoleic acid is synthe-sized endogenously in lactating dairy cows by delta(9)-desaturase. J Nutr. 2000, 130, 2285–2291.
[66] B. A. Corl, L. H. Baumgard, J. M. Griinari, P. Delmonte, K. M.Morehouse, M. P. Yurawecz, D. E. Bauman: Trans-7,cis-9CLA is synthesized endogenously by delta9-desaturase indairy cows. Lipids. 2002, 37, 681–688.
[67] H. G. Enoch, A. Catala, P. Strittmatter: Mechanism of rat livermicrosomal stearyl-CoA desaturase. Studies of the sub-strate specificity, enzyme-substrate interactions, and thefunction of lipid. J Biol Chem. 1976, 251, 5095–5103.
[68] L. Bernard, C. Leroux, Y. Chilliard: Expression and nutritionalregulation of lipogenic genes in the ruminant lactatingmammary gland. Adv Exp Med Biol. 2007, in press.
[69] H. O. Hansen, D. Tornehave, J. Knudsen: Synthesis of milkspecific fatty acids and proteins by dispersed goat mam-mary-gland epithelial cells. Biochem J. 1986, 238, 167–172.
[70] H. O. Hansen, J. Knudsen: Effect of exogenous long-chainfatty acids on individual fatty acid synthesis by dispersedruminant mammary gland cells. J Dairy Sci. 1987, 70, 1350–1354.
[71] T. S. Nielsen, E. M. Straarup, M. Vestergaard, K. Sejrsen:Effect of silage type and concentrate level on conjugatedlinoleic acids, trans-C18:1 isomers and fat content in milkfrom dairy cows. Reprod Nutr Dev. 2006, 46, 699–712.
[72] N. W. Offer, M. Marsden, R. H. Phipps: Effect of oil supple-mentation of a diet containing a high concentration of starchon levels of trans fatty acids and conjugated linoleic acids inbovine milk. Anim Sci. 2001, 73, 533–540.
[73] D. G. Peterson, E. A. Matitashvili, D. E. Bauman: Diet-induced milk fat depression in dairy cows results inincreased trans-10, cis-12 CLA in milk fat and coordinatesuppression of mRNA abundance for mammary enzymesinvolved in milk fat synthesis. J Nutr. 2003, 133, 3098–3102.
[74] L. H. Baumgard, B. A. Corl, D. A. Dwyer, A. Saebo, D. E.Bauman: Identification of the conjugated linoleic acid iso-mer that inhibits milk fat synthesis. Am J Physiol Regul IntegrComp Physiol. 2000, 278, R179–R184.
[75] L. S. Piperova, B. B. Teter, I. Bruckental, J. Sampugna, S. E.Mills, M. P. Yurawecz, J. Fritsche, K. Ku, R. A. Erdman:Mammary lipogenic enzyme activity, trans fatty acids and
conjugated linoleic acids are altered in lactating dairy cowsfed a milk fat-depressing diet. J Nutr. 2000, 130, 2568–2574.
[76] J. J. Loor, K. Ueda, A. Ferlay, Y. Chilliard, M. Doreau: ShortCommunication: Diurnal profiles of conjugated linoleic acidsand trans fatty acids in ruminal fluid from cows fed a highconcentrate diet supplemented with fish oil, linseed oil, orsunflower oil. J Dairy Sci. 2004, 87, 2468–2471.
[77] A. L. Lock, C. Tyburczy, D. A. Dwyer, K. J. Harvatine, F.Destaillats, Z. Mouloungui, L. Candy, D. E. Bauman: Trans-10 octadecenoic acid does not reduce milk fat synthesis indairy cows. J Nutr. 2007, 137, 71–76.
[78] K. J. Shingfield, C. K. Reynolds, B. Lupoli, V. Toivonen, M. P.Yurawecz, P. Delmonte, J. M. Griinari, A. S. Grandison, D. E.Beever: Effect of forage type and proportion of concentratein the diet on milk fatty acid composition in cows givensunflower oil and fish oil. Anim Sci. 2005, 80, 225–238.
[79] A. Saebo, P. C. Saebo, J. M. Griinari, K. J. Shingfield: Effectof abomasal infusions of geometric isomers of 10,12 con-jugated linoleic acid on milk fat synthesis in dairy cows.Lipids. 2005, 40, 823–832.
[80] J. W. Perfield 2nd, A. L. Lock, A. Saebo, J. M. Griinari, D. E.Bauman: Trans9,cis11 conjugated linoleic acid (CLA) redu-ces milk fat synthesis in lactating dairy cows. J Dairy Sci.2005, 88 (Suppl. 1), 211.
[81] J. J. Loor, M. Doreau, J. M. Chardigny, A. Ollier, J. L. Sebe-dio, Y. Chilliard: Effects of ruminal or duodenal supply of fishoil on milk fat secretion and profiles of trans-fatty acids andconjugated linoleic acid isomers in dairy cows fed maizesilage. Anim Feed Sci Technol. 2005, 119, 227–246.
[82] P. V. D. Andrade, P. Schmidely: Effect of duodenal infusion oftrans10,cis12-CLA on milk performance and milk fatty acidprofile in dairy goats fed high or low concentrate diet incombination with rolled canola seed. Reprod Nutr Dev.2006, 46, 31–48.
[83] D. Bauchart, R. Verite, B. Remond: Long-chain fatty aciddigestion in lactating cows fed fresh grass from spring toautumn. Can J Anim Sci. 1984, 64, 330–331.
[84] A. Elgersma, S. Tamminga, G. Ellen: Modifying milk compo-sition through forage. Anim Feed Sci Technol. 2006, 131,207–225.
[85] Y. Chilliard, A. Ferlay, J. Loor, J. Rouel, B. Martin: Trans andconjugated fatty acids in milk from cows and goats con-suming pasture or receiving vegetable oils or seeds. Ital JAnim Sci. 2002, 1, 243–254.
[86] A. Ferlay, B. Martin, P. Pradel, J. B. Coulon, Y. Chilliard:Influence of grass-based diets on milk fatty acid composi-tion and milk lipolytic system in Tarentaise and Montbeliardecow breeds. J Dairy Sci. 2006, 89, 4026–4041.
[87] S. Couvreur, C. Hurtaud, P. G. Marnet, P. Faverdin, J. L.Peyraud: Composition of milk fat from cows selected formilk fat globule size and offered either fresh pasture or acorn silage-based diet. J Dairy Sci. 2007, 90, 392–403.
[88] O. A. Rego, P. V. Portugal, M. B. Sousa, H. J. D. Rosa, C. M.Vouzela, A. E. S. Borba, R. J. B. Bessa: Effect of diet on thefatty acid pattern of milk from dairy cows. Anim Res. 2004,53, 213–220.
[89] S. L. Boken, C. R. Staples, L. E. Sollenberger, T. C. Jenkins,W. W. Thatcher: Effect of grazing and fat supplementationon production and reproduction of Holstein cows. J DairySci. 2005, 88, 4258–4272.
[90] J. K. Kay, J. R. Roche, E. S. Kolver, N. A. Thomson, L. H.Baumgard: A comparison between feeding systems (pas-ture and TMR) and the effect of vitamin E supplementationon plasma and milk fatty acid profiles in dairy cows. J DairyRes. 2005, 72, 322–332.
852 Y. Chilliard et al. Eur. J. Lipid Sci. Technol. 109 (2007) 828–855
[91] G. F. Schroeder, J. J. Couderc, F. Bargo, D. H. Rearte: Milkproduction and fatty acid profile of milk fat by dairy cowsfed a winter oats (Avena sativa L.) pasture only or a totalmixed ration. N Z J Agric Res. 2005, 48, 187–195.
[92] G. F. Schroeder, G. A. Gagliostro, F. Bargo, J. E. Delahoy, L.D. Muller: Effects of fat supplementation onmilk productionand composition by dairy cows on pasture: A review. LivestProd Sci. 2004, 86, 1–18.
[93] T. R. Dhiman, G. R. Anand, L. D. Satter, M. W. Pariza: Con-jugated linoleic acid content of milk from cows fed differentdiets. J Dairy Sci. 1999, 82, 2146–2156.
[94] S. Couvreur, C. Hurtaud, C. Lopez, L. Delaby, J. L. Peyraud:The linear relationship between the proportion of freshgrass in the cow diet, milk fatty acid composition, andbutter properties. J Dairy Sci. 2006, 89, 1956–1969.
[95] G. F. Schroeder, J. E. Delahoy, I. Vidaurreta, F. Bargo, G. A.Gagliostro, L. D. Muller: Milk fatty acid composition ofcows fed a total mixed ration or pasture plus concentratesreplacing corn with fat. J Dairy Sci. 2003, 86, 3237–3248.
[96] A. Lucas, C. Agabriel, B. Martin, A. Ferlay, I. Verdier-Metz,J. B. Coulon, E. Rock: Relationships between the condi-tions of cow’s milk production and the contents of compo-nents of nutritional interest in raw milk farmhouse cheese.Lait. 2006, 86, 177–202.
[97] A. Elgersma, G. Ellen, H. van der Horst, H. Boer, P. R. Dek-ker, S. Tamminga: Quick changes in milk fat compositionfrom cows after transition from fresh grass to a silage diet.Anim Feed Sci Technol. 2004, 117, 13–27.
[98] F. Leiber, M. Kreuzer, D. Nigg, H. R. Wettstein, M. R. L.Scheeder: A study on the causes for the elevated n-3 fattyacids in cows’ milk of alpine origin. Lipids. 2005, 40, 191–202.
[99] M. Collomb, R. Sieber, U. Butikofer: CLA isomers in milk fatfrom cows fed diets with high levels of unsaturated fattyacids. Lipids. 2004, 39, 355–364.
[100] M. Doreau, C. Poncet: Ruminal biohydrogenation of fattyacids originating from fresh or preserved grass. ReprodNutr Dev. 2000, 40, 201.
[101] M. Doreau, M. R. F. Lee, K. Ueda, N. D. Scollan: M�tabo-lisme ruminal et digestibilit� des acides gras des fourrages.12 emes Rencontres Recherches Ruminants, Paris(France). 2005, 12, 101–104.
[102] K. J. Shingfield, P. Salo-Vaananen, E. Pahkala, V. Toivonen,S. Jaakkola, V. Piironen, P. Huhtanen: Effect of forage con-servation method, concentrate level and propylene glycolon the fatty acid composition and vitamin content of cows’milk. J Dairy Res. 2005, 72, 349–361.
[103] W. Steele, R. C. Noble: Changes in lipid composition ofgrass during ensiling with or without added fat or oil. ProcNutr Soc. 1984, 43, 51A.
[104] A. Ferlay, J. P. Andrieu, D. Pomies, W. Martin-Rosset, Y.Chilliard: Effet de l’ensilage enrubann� d’herbe de demimontagne sur la composition en acides gras d’int�retnutritionnel du lait de vache. 9 emes Rencontres Recher-ches Ruminants, Paris (France). 2002, 9, 365.
[105] M. Lourenco, B. Vlaeminck, M. Bruinenberg, D. Demeyer,V. Fieveza: Milk fatty acid composition and associatedrumen lipolysis and fatty acid hydrogenation when feedingforages from intensively managed or semi-natural grass-lands. Anim Res. 2005, 54, 471–484.
[106] G. Jahreis, J. Fritsche, H. Steinhart: Conjugated linoleicacid in milk fat: High variation depending on productionsystem. Nutr Res. 1997, 9, 1479–1484.
[107] K. A. Ellis, G. Innocent, D. Grove-White, P. Cripps, W. G.McLean, C. V. Howard, M. Mihm: Comparing the fatty acidcomposition of organic and conventional milk. J Dairy Sci.2006, 89, 1938–1950.
[108] M. Journet, Y. Chilliard: Influence de l’alimentation sur lacomposition du lait. 1. Taux butyreux: Facteurs g�n�raux.Bulletin Technique CRZV INRA Theix. 1985, 60, 13–23.
[109] J. J. Kennelly: The fatty acid composition of milk fat asinfluenced by feeding oilseeds. Anim Feed Sci Technol.1996, 60, 137–152.
[110] F. Bargo, L. D. Muller, J. E. Delahoy, T. W. Cassidy: Milk re-sponse to concentrate supplementation of high producingdairy cows grazing at two pasture allowances. J Dairy Sci.2002, 85, 1777–1792.
[111] F. Bargo, J. E. Delahoy, G. F. Schroeder, L. D. Muller: Milkfatty acid composition of dairy cows grazing at two pastureallowances and supplemented with different levels andsources of concentrate. Anim Feed Sci Technol. 2006, 125,17–31.
[112] R. J. Dewhurst, W. J. Fisher, J. K. S. Tweed, R. J. Wilkins:Comparison of grass and legume silages for milk produc-tion. 1. Production responses with different levels of con-centrate. J Dairy Sci. 2003, 86, 2598–2611.
[113] B. Vlaeminck, V. Fievez, A. R. J. Cabrita, A. J. M. Fonseca,R. J. Dewhurst: Factors affecting odd- and branched-chainfatty acids in milk: A review. Anim Feed Sci Technol. 2006,131, 389–417.
[114] J. M. Griinari, D. A. Dwyer, M. A. McGuire, D. E. Bauman, D.L. Palmquist, K. V. Nurmela: Trans-octadecenoic acids andmilk fat depression in lactating dairy cows. J Dairy Sci.1998, 81, 1251–1261.
[115] S. Jurjanz, V. Monteils, P. Juaneda, F. Laurent: Variations oftrans octadecenoic acid in milk fat induced by feeding dif-ferent starch-based diets to cows. Lipids. 2004, 39, 19–24.
[116] E. Tsiplakou, K. C. Mountzouris, G. Zervas: Concentrationof conjugated linoleic acid in grazing sheep and goat milkfat. Livest Sci. 2006, 103, 74–84.
[117] J. Rouel, A. Ferlay, J. M. Chabosseau, P. Capitan, P.Gaborit, Y. Chilliard: Effects of fresh raygrass, raygrass hayor alfalfa hay on goat milk yield and composition, includingtrans and conjugated fatty acids. In:Book of Abstracts, 54th
Annual Meeting of European Association for Animal Pro-duction, Rome (Italy) 31 Aug-3 Sep. 2003, Ed. Y. van derHoning, Wageningen Academic Publishers, Wageningen(The Netherlands) 2003, p 349.
[118] M. Ledoux, A. Rouzeau, P. Bas, D. Sauvantt: Occurrence oftrans-C18:1 fatty acid isomers in goat milk: Effect of twodietary regimens. J Dairy Sci. 2002, 85, 190–197.
[119] P. V. D. Andrade, P. Schmidely: Influence of percentage ofconcentrate in combination with rolled canola seeds onperformance, rumen fermentation and milk fatty acidcomposition in dairy goats. Livest Sci. 2006, 104, 77–90.
[120] Y. Chilliard, J. M. Chabosseau, J. Rouel, P. Capitan, C.Gominard, P. Gaborit, P. Juaneda, A. Ferlay: Interactionsbetween forage nature and sunflower or linseed oil sup-plementation on goat milk fatty acids of interest for humannutrition. Multi-function grasslands: Quality forages, animalproducts and landscapes. Proceedings of the 19th GeneralMeeting of the European Grassland Federation, LaRochelle, France, 27–30 May 2002, pp. 548–549.
[121] Y. Chilliard: Dietary fat and adipose tissue metabolism inruminants, pigs, and rodents: A review. J Dairy Sci. 1993,76, 3897–3931.
[122] D. Bauchart, A. Roy, S. Lorenz, J. M. Chardigny, A. Ferlay,D. Gruffat, J. L. S�b�dio, Y. Chilliard, D. Durand: Buttersvarying in trans 18:1 and cis-9,trans-11 conjugated linoleicacid modify plasma lipoproteins in the hypercholester-olemic rabbit. Lipids. 2007, 42, 123–133.
[123] P. L. Schneider, D. Sklan, W. Chalupa, D. S. Kronfeld:Feeding calcium salts of fatty acids to lactating cows. JDairy Sci. 1988, 71, 2143–2150.
Eur. J. Lipid Sci. Technol. 109 (2007) 828–855 Feeding factors, rumen biohydrogenation and milk fatty acids 853
[124] A. S. Atwal, M. Hidiroglou, J. K. G. Kramer, M. R. Binns:Effects of feeding alpha-tocopherol and calcium salts offatty acids on vitamin E and fatty acid composition of cow’smilk. J Dairy Sci. 1990, 73, 2832–2841.
[125] Y. Chilliard, M. Doreau, G. Gagliostro, Y. Elmeddah: Pro-tected (encapsulated or calcium soaps) lipids in dairy cowdiets. Effects on production and milk composition. ProdAnim. 1993, 6, 139–150.
[126] S. A. Mosley, E. E. Mosley, B. Hatch, J. I. Szasz, A. Corato,N. Zacharias, D. Howes, M. A. McGuire: Effect of varyinglevels of fatty acids from palm oil on feed intake and milkproduction in Holstein cows. J Dairy Sci. 2007, 90, 987–993.
[127] D. L. Palmquist, T. C. Jenkins: Fat in lactation rations:Review. J Dairy Sci. 1980, 63, 1–14.
[128] C. Gonthier, A. F. Mustafa, D. R. Ouellet, P. Y. Chouinard, R.Berthiaume, H. V. Petit: Feeding micronized and extrudedflaxseed to dairy cows: Effects on blood parameters andmilk fatty acid composition. J Dairy Sci. 2005, 88, 748–756.
[129] T. C. Jenkins: Fatty acid composition of milk from Holsteincows fed oleamide or canola oil. J Dairy Sci. 1998, 81, 794–800.
[130] J. J. Loor, J. H. Herbein, T. C. Jenkins: Nutrient digestion,biohydrogenation, and fatty acid profiles in blood plasmaand milk fat from lactating Holstein cows fed canola oil orcanolamide. Anim Feed Sci Technol. 2002, 97, 65–82.
[131] J. E. Storry, A. J. Hall, V. W. Johnson: The effects ofincreasing amounts of dietary tallow on milk-fat secretionin the cow. J Dairy Res. 1973, 40, 293–299.
[132] S. G. Onetti, R. D. Shaver, M. A. McGuire, R. R. Grummer:Effect of type and level of dietary fat on rumen fermentationand performance of dairy cows fed corn silage-baseddiets. J Dairy Sci. 2001, 84, 2751–2759.
[133] A. A. AbuGhazaleh, D. J. Schingoethe, A. R. Hippen, K. F.Kalscheur, L. A. Whitlock: Fatty acid profiles of milk andrumen digesta from cows fed fish oil, extruded soyabeansor their blend. J Dairy Sci. 2002, 85, 2266–2276.
[134] H. V. Petit: Digestion, milk production, milk composition,and blood composition of dairy cows fed whole flaxseed. JDairy Sci. 2002, 85, 1482–1490.
[135] T. C. Jenkins, H. G. Bateman, S. M. Block: Butylsoyamideincreases unsaturation of fatty acids in plasma and milk oflactating dairy cows. J Dairy Sci. 1996, 79, 585–590.
[136] T. R. Dhiman, K. V. Zanten, L. D. Satter: Effect of dietary fatsource on fatty acid composition of cow’s milk. J Sci FoodAgric. 1995, 69, 101–107.
[137] M. Doreau, Y. Chilliard: Un cas atypique de chute du tauxbutyreuxdu lait [An atypical case of butterfat dropwith dietssupplemented with vegetable fat]. 6 emes RencontresRecherches Ruminants, Paris (France). 1999, 6, 314.
[138] P. Y. Chouinard, J. Levesque, V. Girard, G. J. Brisson: Diet-ary soybeans extruded at different temperatures: Milkcomposition and in situ fatty acid reactions. J Dairy Sci.1997, 80, 2913–2924.
[139] P. Y. Chouinard, V. Girard, G. J. Brisson: Performance andprofiles of milk fatty acids of cows fed full fat, heat-treatedsoybeans using various processing methods. J Dairy Sci.1997, 80, 334–342.
[140] R. K. McGuffey, D. J. Schingoethe: Whole sunflower seedsfor high producing dairy cows. J Dairy Sci. 1982, 65, 1479–1483.
[141] B. F. McNamee, A. M. Fearon, J. Pearce: Effect of feedingoilseed supplements to dairy cows on ruminal and milkfatty acid composition. J Sci Food Agric. 2002, 82, 677–684.
[142] I. W. McDonald, T. W. Scott: Foods of ruminant origin withelevated content of polyunsaturated fatty acids.World RevNutr Diet. 1977, 26, 144–207.
[143] A. Ferlay, Y. Chilliard, M. Doreau: Effects of calcium saltsdiffering in fatty acid composition on duodenal and milkfatty acid profiles in dairy cows. J Sci Food Agric. 1992, 60,31–37.
[144] F. Akraim, M. C. Nicot, P. Juaneda, F. Enjalbert: Conjugatedlinolenic acid (CLnA), conjugated linoleic acid (CLA) andother biohydrogenation intermediates in plasma and milkfat of cows fed raw or extruded linseed. Animal. 2007, inpress.
[145] H. V. Petit, R. J. Dewhurst, N. D. Scollan, J. G. Proulx, M.Khalid, W. Haresign, H. Twagiramungu, G. E. Mann: Milkproduction and composition, ovarian function, and pros-taglandin secretion of dairy cows fed omega-3 fats. J DairySci. 2002, 85, 889–899.
[146] H. V. Petit: Digestion, milk production, milk composition,and blood composition of dairy cows fed formaldehydetreated flaxseed or sunflower seed. J Dairy Sci. 2003, 86,2637–2646.
[147] P. Weill, B. Schmitt, G. Chesneau, N. Daniel, F. Safraou, P.Legrand: Effects of introducing linseed in livestock diet onblood fatty acid composition of consumers of animalproducts. Ann Nutr Metab. 2002, 46, 182–191.
[148] A. A. Ponter, A. E. Parsy, M. Saade, J. P. Mialot, C. Ficheux,C. Duvaux-Ponter, B. Grimard: Effect of a supplement richin linolenic acid added to the diet of post partum dairycows on ovarian follicle growth, and milk and plasma fattyacid compositions. Reprod Nutr Dev. 2006, 46, 19–29.
[149] M. Focant, E. Mignolet, M. Marique, F. Clabots, T. Breyne,D. Dalemans, Y. Larondelle: The effect of vitamin E sup-plementation of cow diets containing rapeseed and linseedon the prevention of milk fat oxidation. J Dairy Sci. 1998,81, 1095–1101.
[150] E. R. Deaville, D. I. Givens, J. S. Blake: Dietary supple-ments of whole linseed and vitamin E to increase levels ofa-linolenic acid and vitamin E in bovine milk. Anim Res.2004, 53, 3–12.
[151] S. M. Kitessa, S. K. Gulati, G. C. Simos, J. R. Ashes, T. W.Scott, E. Fleck, P. C. Wynn: Supplementation of grazingdairy cows with rumen-protected tuna oil enriches milk fatwith n-3 fatty acids without affecting milk production orsensory characteristics. Br J Nutr. 2004, 91, 271–278.
[152] P. Y. Chouinard, L. Corneau, W. R. Butler, Y. Chilliard, J. K.Drackley, D. E. Bauman: Effect of dietary lipid source onconjugated linoleic acid concentrations in milk fat. J DairySci. 2001, 84, 680–690.
[153] D. P. Bu, J. Q. Wang, T. R. Dhiman, S. J. Liu: Effectivenessof oils rich in linoleic and linolenic acids to enhance con-jugated linoleic acid in milk from dairy cows. J Dairy Sci.2007, 90, 998–1007.
[154] A. L. Lock, P. C. Garnsworthy: Independent effects of diet-ary linoleic and linolenic fatty acids on the conjugatedlinoleic acid content of cows’ milk. Anim Sci. 2002, 74,163–176.
[155] C. Bayourthe, F. Enjalbert, R. Moncoulon: Effects of differ-ent forms of canola oil fatty acids plus canola meal on milkcomposition and physical properties of butter. J Dairy Sci.2000, 83, 690–696.
[156] D. L. Palmquist, J. M. Griinari: Milk fatty acid compositionin response to reciprocal combinations of sunflower andfish oils in the diet. Anim Feed Sci Technol. 2006, 131, 358–369.
[157] L. A. Whitlock, D. J. Schingoethe, A. R. Hippen, K. F. Kal-scheur, R. J. Baer, N. Ramaswamy, K. M. Kasperson: Fishoil and extruded soybeans fed in combination increase
854 Y. Chilliard et al. Eur. J. Lipid Sci. Technol. 109 (2007) 828–855
conjugated linoleic acids in milk of dairy cows more thanwhen fed separately. J Dairy Sci. 2002, 85, 234–243.
[158] F. Destaillats, J. P. Trottier, J. M. Galvez, P. Angers: Analysisof alpha-linolenic acid biohydrogenation intermediates inmilk fat with emphasis on conjugated linolenic acids. JDairy Sci. 2005, 88, 3231–3239.
[159] T. L. Ulbricht, D. A. Southgate: Coronary heart disease:Seven dietary factors. Lancet. 1991, 338, 985–992.
[160] L. Bernard, C. Leroux, M. Bonnet, J. Rouel, P. Martin, Y.Chilliard: Expression and nutritional regulation of lipogenicgenes in mammary gland and adipose tissues of lactatinggoats. J Dairy Res. 2005, 72, 250–255.
[161] Y. Chilliard, S. Ollier, J. Rouel, L. Bernard, C. Leroux: Milkfatty acid profile in goats receiving high forage or highconcentrate diets supplemented, or not, with either wholerapeseeds or sunflower oil. In: Book of Abstracts of the 57th
Annual Meeting of European Association for Animal Pro-duction, Antalya, Turkey, 17–20 September 2006. Ed. Y.van der Honing, Wageningen Academic Publishers,Wageningen (The Netherlands) 2006, p. 296.
[162] P. Schmidely, P. Morand-Fehr, D. Sauvant: Influence ofextruded soybeans with or without bicarbonate on milkperformance and fatty acid composition of goat milk. JDairy Sci. 2005, 88, 757–765.
[163] N. W. Offer, M. Marsden, J. Dixon, B. K. Speake, F. E.Thacker: Effect of dietary fat supplements on levels of n-3poly-unsaturated fatty acids, trans acids and conjugatedlinoleic acid in bovine milk. Anim Sci. 1999, 69, 613–625.
[164] O. A. Rego, H. J. D. Rosa, P. V. Portugal, T. Franco, C. M.Vouzela, A. E. S. Borba, R. J. B. Bessa: The effects ofsupplementation with sunflower and soybean oils on thefatty acid profile of milk fat from grazing dairy cows. AnimRes. 2005, 54, 17–24.
[165] L. Bernard, J. Rouel, C. Leroux, A. Ferlay, Y. Faulconnier, P.Legrand, Y. Chilliard: Mammary lipid metabolism and milkfatty acid secretion in alpine goats fed vegetable lipids. JDairy Sci. 2005, 88, 1478–1489.
[166] A. Nudda, G. Battacone, M. G. Usai, S. Fancellu, G. Pulina:Supplementation with extruded linseed cake affects con-centrations of conjugated linoleic acid and vaccenic acid ingoat milk. J Dairy Sci. 2006, 89, 277–282.
[167] S. M. Kitessa, S. K. Gulati, J. R. Ashes, E. Fleck, T. W.Scott, P. D. Nichols: Utilisation of fish oil in ruminants.II. Transfer of fish oil fatty acids into goats’ milk. Anim FeedSci Technol. 2001, 89, 201–208.
[168] M. R. Sanz Sampelayo, Y. Chilliard, Ph. Schmidely, J. Boza:Influence of type of diet on the fat constituents of goat andsheep milk. Small Rumin Res. 2007, 68, 42–63.
[169] A. Ferlay, J. Rouel, J. M. Chabosseau, P. Capitan, K. Ray-nal-Ljutovac, Y. Chilliard: Interactions between raygrasspreservation and high-oleic sunflower oil supplementationon goat milk composition, including trans and conjugatedfatty acids. In: Book of Abstracts of the 54th Annual Meetingof European Association for Animal Production, Rome,Italy, 31 August–3 September 2003. Ed. Y. van der Honing,Wageningen Academic Publishers, Wageningen (TheNetherlands) 2003, p 350.
[170] M. Doreau, Y. Chilliard, D. Bauchart, B. Michalet-Doreau:Influence of different fat supplements on digestibility andruminal digestion in cows. Ann Zootech. 1991, 40, 19–30.
[171] S. G. Onetti, R. R. Grummer: Response of lactating cows tothree supplemental fat sources as affected by forage in thediet and stage of lactation: A meta-analysis of literature.Anim Feed Sci Technol. 2004, 115, 65–82.
[172] D. E. Bauman, D. M. Barbano, D. A. Dwyer, J. M. Griinari:Technical note: Production of butter with enhanced con-
jugated linoleic acid for use in biomedical studies with ani-mal models. J Dairy Sci. 2000, 83, 2422–2425.
[173] T. R. Dhiman, L. D. Satter, M. W. Pariza, M. P. Galli, K. Alb-right, M. X. Tolosa: Conjugated linoleic acid (CLA) contentof milk from cows offered diets rich in linoleic and linolenicacid. J Dairy Sci. 2000, 83, 1016–1027.
[174] A. Ferlay, P. Capitan, A. Ollier, Y. Chilliard: Interactions be-tween nature of forage and oil supplementation on cowmilk composition. 3. Effects on kinetics and percentages ofmilk CLA and trans fatty acids. In: Book of Abstracts of the54th Annual Meeting of European Association for AnimalProduction, Rome, Italy, 31 August–3 September 2003. Ed.Y. van der Honing, Wageningen Academic Publishers,Wageningen (The Netherlands) 2003, p 120.
[175] A. A. AbuGhazaleh, D. J. Schingoethe, A. R. Hippen, K. F.Kalscheur: Conjugated linoleic acid increases in milk whencows fed fish meal and extruded soybeans for an extendedperiod of time. J Dairy Sci. 2004, 87, 1758–1766.
[176] E. L. Ryhanen, K. Tallavaara, J. M. Griinari, S. Jaakkola, S.Mantere-Alhonen, K. J. Shingfield: Production of con-jugated linoleic acid enriched milk and dairy products fromcows receiving grass silage supplemented with a cereal-based concentrate containing rapeseed oil. Int Dairy J.2005, 15, 207–217.
[177] J. Pottier, M. Focant, C. Debier, G. De Buysser, C. Goffe, E.Mignolet, E. Froidmont, Y. Larondelle: Effect of dietaryvitamin E on rumen biohydrogenation pathways and milkfat depression in dairy cows fed high-fat diets. J Dairy Sci.2006, 89, 685–692.
[178] T. C. Jenkins, V. Fellner, R. K. McGuffey: Monensin by fatinteractions on trans fatty acids in cultures of mixed ruminalmicroorganisms grown in continuous fermentors fed cornor barley. J Dairy Sci. 2003, 86, 324–330.
[179] G. A. Gagliostro, A. Rodriguez, P. Pellegrini, P. M. G. Gatti,R. A. Castaneda, D. Colombo, Y. Chilliard: Efectos delsuministro de aceite de pescado solo o en combinaci�ncon aceite de girasol sobre las concentraciones de �cidolinoleico conjugado (CLA) y omega 3 (n-3) en leche decabra. Rev Argent Prod Anim. 2006, 26, 71–87.
[180] C. Stanton, G. Piredda, N. Offer, S. Banni, Y. Chilliard, L.Leloutre, K. Shingfield, M. Lee, D. Muir: Increasing thecontent of CLA in cheesemilk. In: Proceedings of CheeseWorld Conference, 10–14 May 2006, Munich (Germany)2006, p 1.
[181] Y. Chilliard, J. Rouel, J. M. Chabosseau, P. Capitan, P.Gaborit, A. Ferlay: Interactions between raygrass pre-servation and linseed oil supplementation on goat milkyield and composition, including trans and conjugated fattyacids. In: Book of Abstracts of the 54th Annual Meeting ofEuropean Association for Animal Production, Rome, Italy,31 August–3 September 2003. Ed. Y. van der Honing,Wageningen Academic Publishers, Wageningen (TheNetherlands) 2003, p. 343.
[182] Y. Chilliard, L. Bernard, J. Rouel, A. Ferlay, A. Gaborit, K.Raynal-Ljutovac, A. Lauret: Effet de l’alimentation et de sacomposition en maticre grasse sur la qualit� du lait et desproduits laitiers caprins (aptitude technologique, qualit�sensorielle) et la production d’acides gras pr�sentant unavantage pour la sant� du consommateur. In: Compte-rendu de Fin de Recherche d�p�ration d’une RechercheFinanc�e par le Ministere de la Recherche. INRA-ITPLC,Clermont-Ferrand (France) 2004, pp. 1–39.
[183] L. Bernard, J. Rouel, A. Ferlay, Y. Chilliard: Effects of con-centrate level and starch degradability on milk yield andfatty acid (FA) composition in goats receiving a diet sup-plemented in sunflower oil. In: Book of Abstracts, 56th
Annual Meeting of European Association for Animal Pro-
Eur. J. Lipid Sci. Technol. 109 (2007) 828–855 Feeding factors, rumen biohydrogenation and milk fatty acids 855
duction, 5–8 June. Wageningen Academic Publishers,Wageningen (The Netherlands) 2005, p 161.
[184] Y. Chilliard, J. Rouel, L. Leloutre, E. Bruneteau, P. L. A.Capitan, A. Ferlay: Effects of extruded linseed substitutionto linseed oil and/or soybean meal, on milk yield and fattyacid (FA) composition in goats receiving a high-forage diet.In: Book of Abstracts, 55th Annual Meeting of EuropeanAssociation for Animal Production, Bled (Slovenia) 5–9 Sep2004, Ed. Y van der Honing, Wageningen Academic Pub-lishers, Wageningen (The Netherlands) 2004, p. 135.
[185] Y. Chilliard, J. Rouel, P. Guillouet, K. Raynal-Ljutovac, L.Leloutre, A. Ferlay: Kinetics of responses of goat milk fattyacids to dietary forage:concentrate ratio and/or high dosesof sunflower or linseed oil, or extrudedmixture of seeds. In:Book of Abstracts, 56th Annual Meeting of European Asso-ciation for Animal Production, 5–8 June. Wageningen Aca-demic Publishers, Uppsala (Sweden) 2005, p. 268.
[186] A. Ferlay, J. Rouel, P. Capitan, E. Bruneteau, P. Gaborit, L.Leloutre, Y. Chilliard: Concentrate level and vitamin E sup-plementation do not interact on milk yield and fatty acid(FA) composition in goats receiving alfalfa hay and linseedoil. In: Book of Abstracts, 55th Annual Meeting of European
Association for Animal Production,. Bled (Slovenia) 5–9 Sep 2004, Ed. Y van der Honing, Wageningen AcademicPublishers, Wageningen (The Netherlands) 2004, p. 119.
[187] J. Rouel, A. Ferlay, E. Bruneteau, P. Capitan, K. Raynal-Ljutovac, Y. Chilliard: Interactions between starchy con-centrate and linseed oil supplementation on goat milk yieldand composition, including trans and conjugated fattyacids (FA). In: Book of Abstracts of the 55th Annual Meetingof European Association for Animal Production, Bled, Slo-venia, 5–9 September 2004. Ed. Y. van der Honing,Wageningen Academic Publishers, Wageningen (TheNetherlands) 2004, p. 124.
[188] J. Rouel, E. Bruneteau, P. Guillouet, A. Ferlay, P. Gaborit, L.Leloutre, Y. Chilliard: Goat dairy performances accordingto dietary forage:concentrate ratio and/or high doses ofsunflower or linseed oil, or extruded mixture of seeds. In:Book of Abstracts, 56th Annual Meeting of European Asso-ciation for Animal Production, 5–8 June 2005. WageningenAcademic Publishers, Wageningen (The Netherlands)2005, p. 280.
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