Full Lactation Response of Cows Fed Diets with Different Sources and Amounts of Fiber and Ruminal Degradable Protein1 W. P. WEISS Department of Dairy Science Ohio Agricultural Research and Development Center The Ohio State University Wooster 44691 ABSTRACT Twenty Holstein cows were fed diets based on a mix of haycrop silage (imma- ture orchardgrass or immature alfalfa) and corn silage with a conventional con- centrate (primarily ground ear corn and soybean meal) or a concentrate based on by-products (primarily soyhulls, fish meal, and corn gluten meal). Diets for periods 1 (7 to 134 DIM), 2 (135 to 234 DIM), and 3 (235 to 305 DIM) were 40: 1050, 40:20:40, and 4030:30 haycrop si1age:corn si1age:concentrate (DM ba- sis), respectively. Dietary NDF ranged from 33 to 45%. The species of haycrop forage fed in combination with corn si- lage did not greatly affect milk produc- tion (mean = 28 kg/d), milk composition, nutrient digestibility, or DMI (expressed on a BW basis). Cows fed alfalfa gained more BW than those fed orchardgrass (.18 vs. .03 kg/d). Cows fed by-products produced similar amounts of milk, more milk fat (1.1 vs. .9 kg/d), and had higher DMI (21.4 vs. 19.6 kg/d) but lower BW gains (.03 vs. .18 kg/d) than those fed conventional concentrate. These data showed that a mix of high quality or- chardgrass and corn silage is acceptable for dairy cows and that supplementation strategies are similar for diets based on orchardgrass and those based on alfalfa. (Key words: alfalfa, orchardgrass, neu- tral detergent fiber, by-products) ~ Received October 14, 1994. Accepted April 11, 1995. *Salaries and research support provided by state and federal funds appropriated to the Ohio Agricultural Re- search and Development Center, The Ohio state Univer- sity. Journal Article Number 122-94. Additional suppod provided by the Ohio Dairy Farmer’s Federation Milk Check-off program. Abbreviation key: NDIN = neutral detergent- insoluble N, NSC = nonstructural carbohy- drates. INTRODUCTION Decisions regarding the type of forage to grow and feed on a dairy farm are important and complex. Soil conditions and fertility, ma- nure management systems, forage yields, and the nutritional needs of the cattle must be considered. Adequate information is available concerning agronomic and soil requirements for growth of alfalfa and cool season grasses. However, less information is available regard- ing the nutritional value of alfalfa relative to cool season grasses for dairy cows (3, 9, 28). No data were found that compared production by cows fed either alfalfa or cool season grasses over an entire lactation. Cool season grasses generally contain more NDF than does alfalfa. The NDF in grasses is usually more digestible, but is digested at a slower rate than alfalfa (10). Because of differ- ences in ruminal digestion kinetics between alfalfa and grasses, forage species may in- fluence the response by cows to concentrates differing in carbohydrate source. Concentrates can be categorized based on rate of ruminal availability of energy. Concentrates with large amounts of starch or nonstructural carbohy- drates (NSC), e.g., corn grain, generally pro- vide energy to ruminal microorganisms more quickly than do concentrates with large amounts of NDF, e.g., soyhulls (18). Informa- tion is lacking that compares the responses by cows fed alfalfa or orchardgrass with those for cows fed concentrates differing in carbohy- drate types. Concentration of CP typically is higher for legumes than for grasses; however, variation of CP content within forage categories (grass vs. legume) is probably higher than variation be- tween the categories. Although few data are available, RDP of alfalfa appears to be similar 1995 J Dairy Sci 78:1802-1814 1802
Transcript
Full Lactation Response of Cows Fed Diets with Different Sources and Amounts of Fiber and Ruminal Degradable Protein1
W. P. WEISS Department of Dairy Science
Ohio Agricultural Research and Development Center The Ohio State University
Wooster 44691
ABSTRACT
Twenty Holstein cows were fed diets based on a mix of haycrop silage (imma- ture orchardgrass or immature alfalfa) and corn silage with a conventional con- centrate (primarily ground ear corn and soybean meal) or a concentrate based on by-products (primarily soyhulls, fish meal, and corn gluten meal). Diets for periods 1 (7 to 134 DIM), 2 (135 to 234 DIM), and 3 (235 to 305 DIM) were 40: 1050, 40:20:40, and 4030:30 haycrop si1age:corn si1age:concentrate (DM ba- sis), respectively. Dietary NDF ranged from 33 to 45%. The species of haycrop forage fed in combination with corn si- lage did not greatly affect milk produc- tion (mean = 28 kg/d), milk composition, nutrient digestibility, or DMI (expressed on a BW basis). Cows fed alfalfa gained more BW than those fed orchardgrass (.18 vs. .03 kg/d). Cows fed by-products produced similar amounts of milk, more milk fat (1.1 vs. .9 kg/d), and had higher DMI (21.4 vs. 19.6 kg/d) but lower BW gains (.03 vs. .18 kg/d) than those fed conventional concentrate. These data showed that a mix of high quality or- chardgrass and corn silage is acceptable for dairy cows and that supplementation strategies are similar for diets based on orchardgrass and those based on alfalfa. (Key words: alfalfa, orchardgrass, neu- tral detergent fiber, by-products)
~
Received October 14, 1994. Accepted April 1 1, 1995. *Salaries and research support provided by state and
federal funds appropriated to the Ohio Agricultural Re- search and Development Center, The Ohio state Univer- sity. Journal Article Number 122-94. Additional suppod provided by the Ohio Dairy Farmer’s Federation Milk Check-off program.
Decisions regarding the type of forage to grow and feed on a dairy farm are important and complex. Soil conditions and fertility, ma- nure management systems, forage yields, and the nutritional needs of the cattle must be considered. Adequate information is available concerning agronomic and soil requirements for growth of alfalfa and cool season grasses. However, less information is available regard- ing the nutritional value of alfalfa relative to cool season grasses for dairy cows (3, 9, 28). No data were found that compared production by cows fed either alfalfa or cool season grasses over an entire lactation.
Cool season grasses generally contain more NDF than does alfalfa. The NDF in grasses is usually more digestible, but is digested at a slower rate than alfalfa (10). Because of differ- ences in ruminal digestion kinetics between alfalfa and grasses, forage species may in- fluence the response by cows to concentrates differing in carbohydrate source. Concentrates can be categorized based on rate of ruminal availability of energy. Concentrates with large amounts of starch or nonstructural carbohy- drates (NSC), e.g., corn grain, generally pro- vide energy to ruminal microorganisms more quickly than do concentrates with large amounts of NDF, e.g., soyhulls (18). Informa- tion is lacking that compares the responses by cows fed alfalfa or orchardgrass with those for cows fed concentrates differing in carbohy- drate types.
Concentration of CP typically is higher for legumes than for grasses; however, variation of CP content within forage categories (grass vs. legume) is probably higher than variation be- tween the categories. Although few data are available, RDP of alfalfa appears to be similar
1995 J Dairy Sci 78:1802-1814 1802
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to that of grasses when harvested at similar maturities (2, 10, 14). In vivo data, however, suggest that ruminal metabolism of N differs between cows fed alfalfa and those fed cool season grasses (5, 8). Data for full lactations are unavailable on the influence of supplemen- tal protein source to cows fed alfalfa or or- chardgrass.
The objectives of this study were 1) to compare total lactation performance by cows fed combinations of orchardgrass silage and corn silage or alfalfa silage and corn silage, 2) to compare total lactation performance by cows fed a concentrate mix with relatively rapid rates of carbohydrate and protein availa- bility in the rumen or when fed a concentrate mix with relatively slow rates of carbohydrate and protein availability, and 3) to determine whether interactions existed between type of concentrate and type of forage.
MATERIALS AND METHODS
Cows and ~ i e t s
Sixteen multiparous and 4 primiparous Hol- stein cows were assigned to one of five blocks
based on date of parturition and lactation num- ber. Cows within blocks were assigned ran- domly to one of four treatments. Treatments consisted of a factorial arrangement of two types of haycrop silage (orchardgrass or alfalfa) fed in combination with corn silage and two types of concentrates. The concentrates (Table 1) were either based largely on ingredients (ground ear corn and soybean meal) with rela- tively high concentrations of RDP and NSC or based on ingredients (soyhulls, dehydrated al- falfa meal, fish meal, and corn gluten meal) with relatively high concentrations of RUP and NDF. Diets were balanced to meet NRC (17) recommendations for minerals and vitamins.
Primary growth of orchardgrass was har- vested in the vegetative stage, and regrowth was harvested every 25 to 30 d (grown at Wooster, OH). Orchardgrass came from a sin- gle field that was fertilized with approximately 160 tonneha per yr of liquid (4% DM) dairy manure (split over three applications) and ap- proximately 100 kg/ha per yr of N from am- monium nitrate (one-half applied 40 d prior to first cutting and one-half applied immediately
TABLE 1. Ingredient and nutrient composition of concentrate mixtures fed with alfalfa or orchardgrass silage @M basis).'
Alfalfa Orchardgrass
NSC NDF NSC NDF plus RDP plus RUP plus RDP plus RUP
In = 8. zhmixes included limestone, &calcium phosphate, monosodium phosphate, calcium sulfate, trace mined salt,
3Calculated from NRC (17). 4Neutral detergent-insoluble N.
sodium selenate, copper sulfate. and vitamins A, D. and E.
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after the third cutting). Mean composition of the manure (wet basis) was .2% N (50% of total N was ammonia N), .2% K, and .07% P. Alfalfa (several fields and all cuttings) was harvested in the late bud to early bloom stage of maturity. Both forages were wilted to 40 to 60% DM, chopped at a theoretical length of 1.5 cm, and ensiled in glass-lined steel silos. Silage composition is presented in Table 2.
Cows started on the experiment 7 d after parturition and remained on their treatments until 305 DIM. One cow was dried off at 289 DIM. Two cows had health problems during the peripartum period and did not start the experiment until 12 DIM. One case of clinical mastitis occurred during the experiment; 2 cows had left displaced abomasum, and 1 cow went off feed for approximately 7 d for un- known reasons. Health problems appeared to be unrelated to treatment, and data from all cows and all days were included in the ana- lyses.
Lactations were divided into three periods. Period 1 consisted of 7 through 134 DIM, period 2 lasted from 135 through 234 DIM, and period 3 lasted from 235 through 305 DIM. During period 1, cows were fed diets (DM basis) consisting of haycrop si1age:corn si1age:concentrate. 40: 1050; period 2 diets were 40:20:40; and period 3 diets were 40:30:
30. The haycrop silage constituted 80, 67, and 57% of the forage DM component during peri- ods l, 2, and 3, respectively. Nutrient compo- sition for diets in each period is presented in Table 3.
Cows were housed in individual tie stalls throughout the experiment. Diets were fed as a TMR once daily for ad libitum consumption. Cows were weighed at the start of the experi- ment and at 30d intervals. Change in BW was calculated each month and then averaged for each period and for the entire lactation.
Dlgestibillty Experiments
Three blocks of cows were used to deter- mine apparent total tract digestibility of nutrients. Cows (by blocks) were moved into digestion stalls at approximately 70, 170, and 270 DIM. Cows remained in the stalls for 4 d. Feed offered, orts, and total output of feces, urine, and milk were recorded, sampled daily, and composited (28). At the conclusion of the digestion experiment, cows were moved back into tie stalls.
Sampling and Chemical Analyses
Haycrop silages were sampled weekly and composited quarterly (8 samples per forage). Weekly samples were analyzed for DM (4) to
TABLE 2. Nutrient composition and fermentation characteristics of silages @M basis).'
Alfalfa Orchardgrass Corn silage
X SD X SD X SD - - -
Nutrients DM, % Ash, % CP, % NDIN? % of N ADIN, 96 of N NDF, % ADF, % Lignin, % ca, % p, 96 I C %
PH Fermentation measures
Lactic acid, % Acetic acid, % Butyric acid, % NHq N, 96 of N
1n = 9 for nutrients, and n = 8 for fermentation measures. ZNeutral detergent-insoluble N.
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adjust TMR for changes in DM. The com- posited samples were extracted with water and analyzed for pH, lactic acid, and VFA (28). Nutrient composition of haycrop silages, corn silage, and concentrates (Tables 1 and 2) was determined on samples collected during the digestion trials (approximately one every 3 mo for a total of 9 samples during the experiment). Feeds, orts, and feces were analyzed for DM, NDF, ADF, acid detergent lignin (sulfuric acid method), ash, neutral detergent-insoluble N P I N ) , and ADIN (28). The NSC concentra- tions were calculated as [lo0 - (NDF + CP + ash + ether extract) + (NDIN x 6.25)]. Refer- ence values for ether extract were used (17). All analyses, except for DM, were conducted on lyophilized samples. The NDF procedure included a-amylase but not sodium sulfite. Milk was sampled every 2 wk and analyzed for protein and fat using infrared spectroscopy (Ohio Ag Services, Powell, OH). Ruminal fluid was sampled via stomach tube approximately 4
TABLE 3. Nutrient composition (DM basis) of diets.1
h after feeding from 4 cows per treatment (each period) and analyzed for VFA (28).
Statistical Analyser
All data were analyzed using a model for a randomized complete block design. The model included block, forage type (1 df), concentrate type (1 df), forage by concentrate interaction (1 df), and error. The degrees of freedom for block and error for digestibility data were 2 and 6, for ruminal fluid data were 3 and 9, and for production data were 4 and 12. respec- tively. Digestibility, ruminal fluid, and produc- tion data were analyzed by period. Production data also were averaged for the entire lactation and analyzed using the previously described model. The general linear models procedure of SAS (21) was used for all analyses. Correla- tions among variables and regression equations were determined using the regression proce- dure of SAS (21).
Alfalfa Orcharderass
Nutrient NSC NDF NSC NDF plus RDP* plus RUP plus RDP plus RUP
'Diets (DM basis) fed during periods I , 2, and 3 were 40:10:50, 40:20:40, and 40:20:30 haycrop silage:com silage:
2NSC plus RDP = Concentrate of primarily ear corn and soybean meal; NDF plus RUP = concentrate of primarily
3Nonseuctural cahohydrates (NSC) calculated as 100 - @lDF + CP + ash + ether ex-) + (NDIN x 6.25). 4The NEL value calculated as [(OM digestibility + 1.25 x ether extract) x .0245] - .12.
concentrate. respectively.
soyhulls, dehydrated alfalfa, fish meal, and corn gluten meal.
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RESULTS
Forage Quality
Mean annual yield of orchardgrass DM (not replicated) was approximately 8.6 tonneha. Approximately 420, 110, and 420 kg/ha of N, P, and K, respectively, were applied to the orchardgrass annually from manure and fer- tilizer, and approximately 300, 40, and 440 kgl ha of N, P, and K, respectively, were removed annually by harvesting. Nutrient composition and fermentation measures for corn silage were typical (Table 2). The concentration of CP was typical for alfalfa harvested at the late bud to early bloom stages of maturity, but concentra- tions of NDF and ADF were higher than ex- pected. Concentrations of CP and NDF in or- chardgrass were typical, but ADF and lignin concentrations were higher than anticipated. Growing conditions during this experiment were hotter and drier than normal, which may have influenced chemical composition (25). The high K concentrations in the orchardgrass and alfalfa are probably a result of the large amount of manure applied to the fields. The alfalfa fermented normally and had a low con- centration of butyric acid, a moderate amount
of NH3, and a normal concentration of ADIN. Orchardgrass silage had moderately high con- centrations of ADIN, NH3, acetic acid, and butyric acid compared with recommended con- centrations (9). The DM content (41%) of the orchardgrass silage probably precluded a clos- tridial fermentation. The most likely explana- tion for these elevated concentrations is poor consolidation and air entrapment (29). Orchard- grass came from a single field (3.6 ha). Yields from some cuttings were quite low ( 4 3 tonne per cutting, as-harvested basis), which added little to the total silage mass and probably resulted in poor compaction. Another possibil- ity is that manure application to the growing crop inoculated the forage with undesirable microorganisms (19).
Production Data
With the exception of DMI (as percentage of BW), no interactions between forage species and concentrate type were observed for production data; therefore, only main effect means are presented. Forage species had no effect on milk production, milk composition, or DMI during period 1 (Table 4). Cows fed alfalfa weighed more than those fed orchard-
TABLE 4. Production data for cows fed orchardgrass (OG) or alfalfa (ALF) silages with two types of concentrates during period 1 (7 to 134 DIM). Diets @M basis) were 40:10:50 haycrop si1age:corn silage:concentrate.'
Item
Concentrate (e P <3
NSC NDF Forage 0
OG ALF plus RDP plus RUP SE F C
Cows, no. BW, kg DMI, kg/d DMI, 9% of BW BW Change, kg/d Milk, kgld 4% FCM, kg/d Milk fat
kg/d
% kdd
%
Milk protein
10 585
19.6 3.36 -.36
32.8 29.1
3.30 1.07
3.00 .97
10 63 1 20.6
3.26 -.19
33.0 28.8
3.14 1.04
2.97 .98
~~
10 10 604 616
19.2 21.0 3.19 3.43 -.20 -.31
33.9 31.8 27.9 30.0
2.84 3.60 .96 1.16
2.90 3.07 .98 .98
15 .5 .05 .10
1.4 1.1
.09
.04
.04
.04
.06 . . .
. . . .02
. . . .01
. . . . . .
. . . . . .
. . . .20
. . . .o I
. . . .01
. . . .02
. . . . . . ~~ ~ ~~~
'Most interactions between forage and concentrate were not significant (P > .25); therefore, only main effect means
lNSC plus RDP = Concentrate of primarily ear corn and soybean meal; NDF plus RUP = concentrate of primarily
'Probability that differences are due to chance; P > .25 are not shown.
are presented.
soyhulls, dehydrated alfalfa fish meal, and corn gluten meal.
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TABLE 5. F'roduction data for cows fed orchardgrass (ffi) or alfalfa (ALE) silages with two types of concentrates during period 2 (135 to 234 DIM). Diets (DM basis) wen 40:20:40 haycrop silage:corn silage:concentrate.'
Concentrate (@ P <3
NSC NDF Forage 0 Item OG ALF plus RDP plus RUP SE F C F x C
'Most interactions between forage and concentrate were not significant (P > 3); therefore, only main effect means
ZNSC plus RDP = Concentrate of primarily ear corn and soybean meal; NDF plus RUP = concentrate of primarily
3Probability that differences are due to chance; P > .25 are not shown.
~IE presented.
soyhulls, dehydrated alfalfa, fish meal, and corn gluten meal.
TABLE 6. Production data for cows fed orchardgrass (ffi) or alfalfa (ALF) silages with two types of concentrates during period 3 (235 to 305 DIM). Diets (DM basis) were 40:30:30 haycrop silage:corn silage:concentrate.'
'Most interactions between forage and concentrate were not significant (P > .25); therefore, only main effect means
2NSC plus RDP = Concentrate of primarily ear corn and soybean meal; NDF plus RUF' = concentrate of primarily
Vrobability that differences are due to chance; P > .25 are not shown.
are presented.
soyhulls, dehydrated alfalfa meal, fish meal, and corn gluten meal.
Journal of Dairy Science Vol. 78, No. 8, 1995
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grass, but those cows started the experiment with greater BW (cows were not blocked by BW). During periods 2 and 3, cows fed alfalfa had greater DMI than did cows fed orchard- grass (Tables 5 and 6); however, when DMI was expressed as a percentage of BW, no differences were observed. Milk production and composition were not affected by forage species during periods 2 and 3. Milk produc- tion and composition over the entire lactation were not different between cows fed alfalfa and those fed orchardgrass (Table 7). Cows fed alfalfa had greater DMI than those fed orchard- grass, but DMI was not different when ex- pressed on a BW basis. Change in BW during each period was not statistically different be- tween cows fed orchardgrass and those fed alfalfa; however, over the entire lactation, cows fed alfalfa gained more (P < .05) BW than those fed orchardgrass.
Cows fed the NDF plus RUP concentrate had higher DMI and DMI as a percentage of BW than did cows fed NSC plus RDP (Tables 4, 5, 6, and 7). Milk production was not af- fected by type of concentrate during any period or over the entire lactation. Concentration and production of milk fat were higher for cows fed NDF plus RUP than for those fed NSC
plus RDP during all periods and over the entire lactation. Because of increased production of milk fat, production of FCM by cows fed NDF plus RUP tended to be higher (P < .12) than for cows fed NSC plus RDP for the entire lactation. Concentration of milk protein was higher (P < .02) for cows fed NDF plus RUP than for cows fed NSC plus RDP during period 1. During periods 2 and 3 and for the entire lactation, milk protein production and percentage did not differ between concentrate types. Change in BW was not affected by concentrate when data were analyzed by period, but, for the entire lactation, cows fed NSC plus RDP gained more BW than did cows fed NDF plus RUP.
Interactions between forage species and concentrate type were observed for DMI ex- pressed as a percentage of BW during periods 2 and 3 and over the entire lactation. The interaction was apparently caused by depressed DMI for cows fed alfalfa and NSC plus RDP. Generally, DMI (as percentage of BW) was much higher for cows fed NDF plus RUP with alfalfa (3.44) than for those fed NSC plus RDP with alfalfa (3.06). For cows fed orchardgrass, DMI (percentage of BW) was similar between NDF plus RUP and NSC plus RDP (3.44 vs. 3.25 for entire lactation).
TABLE 7. Production data for cows fed orchardgrass (OG) or alfalfa (ALF) silages with two types of concentrates during entire. lactation (7 to 305 DW.1
Concentrate (Q Forage 0 P <3
NSC NDF Item OG ALF plus RDP plus RUP SE F C F x C
'Most interactions between forage and concentrate were not significant (P > .25); therefore, only main effect means
ZNSC plus RDP = Concentrate of primarily ear corn and soybean meal; NDF plus RUP = Concentrate of primarily
3Probability that differences are due to chance; P > .25 axe not shown.
axe presented.
soyhulls, fish meal, and corn gluten meal.
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Dlgestlbllliy Data
No interactions between main effects were observed; main effect means for digestibility data are presented in Table 8. Forage species had no consistent effect on digestibility of most nutrients. In period 1, OM from diets with alfalfa was more digestible than that from diets with orchardgrass. No differences were observed in periods 2 and 3. Calculated across periods, the mean OM digestibility for or- chardgrass diets was 64.6%. and the mean OM digestibility for alfalfa diets was 65.5%. Di- gestibility of NDF and cellulose tended to be greater for orchardgrass than for alfalfa diets. Across periods, the mean NDF digestibility was 54.5% for orchardgrass and 50.9% for alfalfa. The mean cellulose digestibility was 64.3% for orchardgrass and 60% for alfalfa.
Digestibility of N (across periods) was higher by cows fed alfalfa than by those fed orchard- grass (60 vs. 53.4'37, respectively). Digestibility of N was related negatively to ADIN concen- trations of the diets (N digestibility = 66.2 - 1.4 x ADIN (as percentage of N); r2 = .33; P <
Digestibility of fiber fractions (NDF, ADF, and cellulose) tended to be higher by cows fed NDF plus RUP than by cows fed NSC plus RDP (Table 8). Digestibility of other nutrients was essentially unaffected by concentrate type.
.Ol).
Rumlnal VFA Data
In general, few interactions were found be- tween forage species and concentrate type for VFA data (Table 9). In all periods, the molar percentage tended to be higher for propionate
TABLE 8. Digestibility (percentage) of nutrients by cows fed diets containing orchardgrass (OG) or alfalfa silage (ALF) with two types of concentrates.'
*Most interactions between forage and concentrate were not significant (P z .25); therefore, only main effect means
2NSC plus RDP = Concentrate of primarily ear corn and soybean meal; NDF plus RUP = concentrate of primarily
3Probability that differences are due to chance; P > .25 are not shown. 4Diets (DM basis) consisted of 40:1050,40:2040, and a 3 0 3 0 haycrop si1age:com si1age:concentrate during periods
are presented.
soyhulls, fish meal, and corn gluten meal.
1, 2, and 3, respectively.
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and lower for acetate for cows fed alfalfa than for those fed orchardgrass. Subsequently, the acetate:propionate ratio tended to be higher for cows fed orchardgrass than for those fed al- falfa. Butyrate responses to forage species were variable across periods. In periods 1 and 3, the molar percentage of acetate tended to be higher, and propionate tended to be lower, for cows fed NDF plus RUP than for cows fed NSC plus RDP.
Energy Balance
Net energy used for maintenance, BW change, and FCM production was calculated using standard NRC (17) equations (Table 10). The NEL concentration in the diets was esti- mated by converting digestible OM to TDN (24) and then converting TDN to NEL (15). Calculated energy use accounted for 93 to 104% of calculated NEL intake. During period 1, cows were in negative energy balance.
Productive NEL (BW change plus FCM) and total NEL use were not affected by forage species or concentrate type in period 1. Results were similar for period 2. In period 3, cows fed alfalfa used more (P < .04) NEL for productive purposes than did cows fed or- chardgrass. For the entire lactation, cows fed alfalfa used more NEL for maintenance and BW gain than did cows fed orchardgrass. Cows fed NDF plus RUP used more NEL for FCM and less NEL for BW gain than those fed NSC plus RDP. The amount of NEL used for productive purposes was similar between con- centrate types.
DISCUSSION
The general lack of interactions between forage species and concentrate type suggested that the response by dairy cows to different types of supplemental carbohydrate and pro- tein was generally similar when cows were fed
TABLE 9. Ruminal VFA of cows fed alfalfa (AW) or orchardgrass (OG) with two types of concentrates.'
*Most interactions between forage and concentrate were not significant (P > .25); therefore, only main effect means
2NSC plus RDP = Concentrate of primarily ear corn and soybean meal; NDF plus RUP = concentrate of primarily
3Probability that differences are. due to chance; P > .25 are not shown. 4Diets (DM basis) fed were 40:10:50, 40:20:40, and 40:30:30 haycrop silage:com si1age:concentrate during periods 1,
an? presented.
soyhulls, fish meal, and corn gluten meal.
2, and 3, respectively.
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combinations of immature orchardgrass silage and corn silage or immature alfalfa silage and corn silage.
Concentrate type had a greater influence on diet composition than did species of haycrop forage. For all periods, orchardgrass diets (averaged across concentrate types) contained about 2 percentage units more NDF and 4 percentage units less NSC than did alfalfa diets. The NSC plus RDP diet (averaged across forage species) contained 6 to 11 percentage units less NDF and ADF and 7 to 11 percent- age units more NSC than did the NDF plus RUP diets. Similarly, concentrate type had a greater influence on digestibility, ruminal fer- mentation, and cow performance than did for-
age species. In general, cows fed NDF plus RUP consumed more DM, produced more FCM, produced milk with a higher fat percent- age, and gained less BW than did cows fed NSC plus RDP. Digestibility of fiber compo- nents (NDF, ADF, and cellulose) was higher by cows fed NDF plus RDP than by cows fed NSC plus RUP. The difference in fiber diges- tion may have been caused by reduced nega- tive associative effects (lower NSC in the NDF plus RUP diets) or by the different sources of fiber among the diets.
By design, the effect of concentrate cannot be ascribed specifically to carbohydrate or pro- tein source, but most of the results obtained in this experiment (changed milk fat percentage
TABLE 10. Calculated net energy balance of cows fed orchardgrass (OG) or alfalfa (ALF) silage with two types of concentrates. 1
Concentrate (9 P <3 - NSC NDF
Forage 0 Item OG ALF plus RDPplus RUP SE F C F x C
Period 1 (7 to 134 DIM) BW Change: McaVd FCM.5 Mcal/d Total N E L , ~ McaVd Rod. NEL? McaVd
Period 2 (135 to 234 DIM) BW Change, McaVd FCM, McaVd Total NEL, M d d hod. NEL. McaVd
Period 3 (235 to 305 DIM) BW Change, M c d d FCM, M d d Total NEL, M d t d Rod. NEL, McaVd
Entire lactation BW Change, McaVd FCM, McaVd Total NEL, M d d Prod. NET. McaVd
-1.6 -.9 21.5 21.3 29.5 30.4 20.0 20.4
1.3 1.4 18.1 19.1 29.0 30.8 19.4 20.5
2.0 4.1 14.2 15.8 26.1 30.6 16.2 20.0
.2 1 .o 18.7 19.3 28.6 30.6 18.9 20.3
-1 .o 21.7 29.4 19.7
1.6 17.6 29.3 19.3
3.9 14.0 28.2 17.9
1 .o 18.2 29.1 19.1
-1.5 22.2 30.5 20.7
1 .o 19.6 30.6 20.6
2.3 16.0 28.6 18.3
.2 19.9 30.1 20.1
.5
.8 1 .o .9
.4
.9
.7
.6
1 .1 .9
1 . 1 1.1
.2
.8
.7
.7
. . . . . . . . .
. . . .20 . . .
. . . . . . . . .
. . . . . . . . .
. . . . . . .16
. . . .15 . . .
. l l . . . . . .
. . . .18 . . .
.18 . . . . . .
.23 .16 . . .
.02 , . . . . .
.04 . . . . . .
.04 .04 . . .
. . . .I4 . . .
.08 . . . . . .
.19 . . . . . . Y
1Most interactions between forage and concentrate were not significant (P > .25); therefore, only main effect means
2NSC plus RDP = Concentrate of primarily ear corn and soybean meal; NDF plus RUP = concentrate of primarily
SProbability that differences an due to chance; P > .25 are not shown. ~ N E L for BW gain = Gain, kilogram x 5.12; NEL for BW loss = loss, kilogram x 4.92 (17). S N E L for FCM = FCM, kilogram x .74 (17). 6Total NEL use = Maintenance + BW change + FCM; Maintenance = .08 x BW.75. 7Prod. energy = Energy used for productive purposes; FCM + BW change.
an presented.
soyhulls, fish meal, and corn gluten meal.
Journal of Dairy Science Vol. 78, No. 8, 1995
1812 WEISS
and altered fiber digestibility) suggested a car- bohydrate effect. Previous experiments (6, 12, 20, 22, 23) generally have found that cows fed diets based on grass with fibrous concentrates had increased milk fat production, milk fat percentage, or both compared with those fed starchy concentrates, which is in agreement with the results from the present experiment. Milk production was generally not affected (6, 20, 22) by type of carbohydrate in the concen- trate, but Valk et al. (23) and Huhtanen (11) reported higher milk production, and Jackson et al. (12) reported lower milk production, from cows fed starchy concentrates than from cows fed fibrous concentrates with grass-based diets. Results have been variable when fibrous con- centrates were compared with starchy concen- trates in diets with alfalfa as the predominant forage source. Nakamura and Owen (16) reported that, when soyhulls replaced corn, cows produced milk with increased fat percent- age; MacGregor et al. (13) reported no effect. Both studies found no difference in milk production or DMI when cows were fed starchy concentrates or fibrous concentrates. Responses to RUP have been variable. Produc- tion of milk and milk protein often increased when diets based on grass were supplemented with RUP (9). Milk production by cows fed alfalfa silage diets often increased when RUP was supplemented (7). The increased milk pro- tein percentage during period 1 by cows fed NDF plus RUP might have been a response to RUP, but the increased percentage might also have been caused by differences in milk production because production of milk protein was not affected by concentrate. Supplemental RUP usually did not affect milk fat percentage; in the current study, milk fat percentage was higher for cows fed NDF plus RUP than for those fed NSC plus RDP.
The most consistent difference between cows fed alfalfa and those fed orchardgrass was DMI. Cows fed alfalfa consumed more DM and NEL than did cows fed orchardgrass. Most of that difference was caused by differ- ences in BW between the two groups. Intake expressed on a BW basis (Tables 4, 5, 6, and 7) or metabolic body size basis (data not shown) was not different between forage treatments. Calculated NEL balance data (Table 9) sup- ported the conclusion that BW, not diet com- position, was primarily responsible for differ-
ences in DMI between cows fed alfalfa and those fed orchardgrass. Only during period 3 did cows fed alfalfa have more NEL available for productive purposes (FCM production and BW change) than those fed orchardgrass. Most of that difference was caused by differences in BW gain. Cows fed alfalfa lost less BW during early lactation and gained more BW during late lactation than did cows fed orchardgrass. Experiments conducted by the USDA (26, 27) found that alfalfa was more efficiently utilized for BW gain than was orchardgrass. Ruminal VFA data from the present experiment support the data for BW gain. Cows fed alfalfa had lower molar percentages of acetate, higher per- centages of propionate, and lower A:P ratios. Glenn et al. (8) suggested that one reason alfalfa had a higher efficiency for BW gain than orchardgrass was because of increased ruminal production of propionate.
The exact reason that cows fed alfalfa con- sumed more NEL during period 3 than did cows fed orchardgrass could not be determined from this experiment. The design of this ex- periment precludes comparisons among peri- ods (stage of lactation was confounded com- pletely with forage to concentrate ratio). Diets fed during period 3 contained more NDF and more forage (70% of DM) than diets fed during periods 1 and 2 (50 and 60% of DM, respec- tively). Ruminants almost always consumed more alfalfa than grass (harvested at similar maturities) when forage constituted the entire diet (1). In a previous experiment (28), Weiss and Shockey reported no differences in intake of digestible DM between cows fed orchard- grass and cows fed alfalfa (no other forages were fed) when diets contained 40 or 60% concentrate; when diets contained 20% con- centrate, cows fed alfalfa consumed more digestible DM than did cows fed orchardgrass.
Cows fed NDF plus RUP consumed more DM and tended to consume more NEL throughout the experiment than did cows fed NSC plus RDP. Regression analysis found that NDF content of the diet was correlated posi- tively with DMI (expressed on a BW basis). Regression equations for DMI as percentage of BW were 2.49 + .02 x NDF (I? = .20; P < .OS) for period 1, 1.97 + .038 x NDF (9 = .21; P c .a) for period 2, and 1.39 + .039 x NDF for period 3. Why DMI by cows fed NDF plus RUP was greater than DMI by cows fed NSC
Journal of Dairy Science Vol. 78. No. 8, 1995
SOURCE AND AMOUNT OF DIETARY FIBER 1813
plus RDP is not known. A plausible explana- tion is that the NDF plus RUP diets resulted in a more stable ruminal environment (supported by increased percentage of milk fat and higher fiber digestibility) than did the NSC plus RDP diets.
CONCLUSIONS
Total 305-d milk production averaged 8900 kg (SD = 1230) for multiparous cows and 7300 kg (SD = 1400) for primiparous cows. Diets that contained 40% high quality orchardgrass silage or 40% high quality alfalfa silage were essentially equal when concentrate constituted at least 40% of dietary DM (corn silage made up the remainder of the diet). Cows fed NDF plus RUP produced about 50 kg more milk fat, gained approximately 45 kg less BW, and consumed approximately 550 kg more DM during a 305-d lactation than did cows fed NSC plus RDP. Essentially no interactions were observed between forage species and concentrate type. Data from experiments using high quality alfalfa and corn silage may be applicable to situations in which high quality orchardgrass and corn silage are fed.
ACKNOWLEDGMENTS
The author thanks B. A. Amiet, J. Durst, M. E. Koch, D. Mengel, and M. Messman for technical assistance.
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