Growth, Digestive Capability, Carcass, and Meat Characteristics of Bison bison, Bos taurus, and Bos X Bison112

R. M. Koch”, H. G. Jungt93, J. D. Crouset, V. H. Varelt, and L. V. Cundifft

*Department of Animal Science, University of Nebraska, Lincoln 68583-0908 and +Roman L. Hruska U.S. Meat Animal Research Center, ARS, USDA, Clay Center, NE 68933

ABSTRACT: Three experiments involving 39 Bos tuurus, 14 Bison bison, and 20 Bos x Bison fed diets differing in proportions of roughage and concentrate to evaluate growth, digestive capability, carcass, and meat characteristics are reported. Bos taurus con- sumed more ( P < .05) feed per day and gained more ( P < .05) rapidly than bison or Bos x Bison except during a period of extremely cold weather. Efficiency of gain was similar for all species types. There was no tendency for bison or Bos x Bison to gain more than Bos tuurus on the higher-roughage diets. Bison and Bos x Bison had higher ( P < . l0 to .O 1) digestion coefficients for all components evaluated (i.e., DM, CP, GE, NDF, hemicellulose, and cellulose). Species x diet interactions were not significant, indicating that the higher digestion coefficients of bison were not specific to high-roughage diets. Bison and their

hybrids had more ( P < -05) lean meat and less ( P < .O 1) fat trim in all wholesale cuts except the chuck and rib cuts. Fat thickness at the 12th rib of bison was higher ( P .01) than that of Bos taurus because most of the carcass fat of bison is located over the thoracic area. Bison and Bos x Bison had higher ( P < . O 1) dressing percentages and a lower ( P < .01) proportion of their carcass in the hindquarter than Bos taurus. Shear force and sensory tenderness scores indicated bison were more ( P < .05) tender and had a flavor different ( P < .01) from that of Bos taurus. Bison and Bos x Bison had more ( P < .O 1) cholesterol in the longissimus muscle and less ( P < .05) in the subcutaneous fat than Bos taurus. Bison had a lower ( P < .01) percentage of white and higher percentage of intermediate muscle fibers than Bos taurus with essentially no difference in percentage of red fibers.

Key Words: Bison, Cattle, Growth Rate, Digestion, Carcass Composition, Meat Characteristics

Introduction

The American buffalo, Bison bison, and the domes- tic bovine, Bos taurus, represent two species of the bovine family that evolved under different environ- mental conditions. There has been much interest in these species and hybrids among them t o find animal types that are better adapted to climatic and economic conditions of the northern temperate zones. The early reports of Jones (1907), Boyd (1908, 19141, and Goodnight ( 19 14) primarily described the perceived virtues of “catalo,” a name given by “Buffalo” Jones to crosses of cattle and bison, and the fertility problems

‘Published as paper no. 10635, Journal Ser., Nebraska Agric. Res. Div., Univ. of Nebraska, Lincoln 68583-0908.

2Appreciation is expressed to Robert Ellis, Fort Niobrara Wildlife Refuge, Valentine, NE for making bison available for this research.

3Present address: USDNARS Plant Science Research, 411 Borlaug Hall, Univ. of Minnesota, St. Paul 55108.

Received February 25, 12994. Accepted December 28, 1994.

J . Anim. Sci. 1995. 73:1271-1281

encountered with their crossing. A long-term experi- ment by the Canada Department of Agriculture (Deakin et al., 1935; Logan and Sylvestre, 1950; Peters, 1958) has provided the primary evidence on the use of bison in meat production. Their results indicated extreme problems with maintaining a high percentage of bison in crosses and getting satisfactory fertility in males. There continues to be a paucity of experimental documentation of growth, digestive capability, and carcass characteristics of bison or their interspecific crosses. It has been reported that bison utilize forages, especially low-quality forages, better than Bos taurus (e.g., Richmond et al., 1977; Schaefer et al., 1978). Previous research at the U.S. Meat Animal Research Center (e.g., Koch et al., 1976, 1979, 1982) and other research centers has established that Bos breeds and their crosses differ significantly in many carcass characteristics. Bison have not been adequately evaluated. The two species differ distinctly in conformation, and bison normally have 14 ribs instead of the 13 found in Bos taurus; thus, the possibility that Bison have a larger fraction of their muscle mass in the loin deserves evaluation. Cutout

1271

1272 KOCH ET AL.

data are needed to clarify differences in cut composi- tion and distribution of Bos taurus and bison. Three experiments were conducted to evaluate differences between Bos taurus ( BOS), Bison bison ( BIS), and Bos x Bison ( BHY).

Experimental Procedures

Experimentation with bison or bison hybrids presents unique challenges in obtaining animals of known age and ancestry and in learning husbandry practices necessary t o incorporate the animals into experimental protocols. Three experiments reported here are serendipitous efforts to cope with these challenges. An initial objective was to determine whether Bos taurus, Bos indicus, and Bison bison differed in their intake, growth, efficiency, and diges- tive ability on forage and concentrate diets. The first experiment included Brahman obtained from the Subtropical Agricultural Research Station, Brooks- ville, Florida, and bison from the Fort Niobrara Wildlife Refuge, Valentine, Nebraska. Husbandry aspects associated with the large range in weight of animals and difficulties in getting bison adapted to individual feeding headgates resulted in changes of procedure and objectives. Pen feeding of a moderate- density diet was substituted and digestion trials were eliminated. Subsequently, Brahman were not used because they lacked adaptation to the cold climate. The results of Brahman were not reported here but were summarized by Koch et al. ( 1988). While investigating reproductive development and blood parameters of bison hybrids in a South Dakota herd, Charolais x bison calves were located. These calves were used in the second experiment as a means of evaluating bison inheritance. The hybrids adapted to the individual feeding headgates and husbandry experience was gained; this led to the inclusion of bison with bison hybrids in the third experiment.

Experiment 1

Growth Characters. The first experiment involved 12 Hereford calves born in March and April in the Hereford herd at the US . Meat Animal Research Center and 10 bison calves born in May, June, and July at the Fort Niobrara Wildlife Refuge, Valentine, Nebraska. All animals were castrated and bison were dehorned. The period from late September until January 28 was used t o adjust the animals to the pens and diet t o be used for the 224-d feeding trial, Animals were placed in pens, segregated by species, of five or six animals and fed the following moderate-density diet (ME, 2.69 Mcalkg): corn silage (66%), corn (22%), and a soybean and mineral supplement ( 12%), on a dry matter basis.

After the 224-d feeding trial, animals were con- tinued on the same diet until slaughter. The Bos

taurus were slaughtered in two groups (after 233 and 246 d on feed) based on the time when pens reached an average weight of 520 kg. The bison were younger, smaller, and varied greatly in weight when placed on feed and in subsequent rate of gain. Therefore, bison were slaughtered in three groups (after 246, 267 and 413 d on feed). Seven bison in the first two groups averaged 433 kg when slaughtered. Three bison in the third group averaged 384 kg and, though lighter, seemed to have as much fat cover as those slaughtered earlier. A slaughter weight of 430 kg was thought to be approximately comparable in stage of maturity based on estimates of mature weights of 500 kg for Hereford cows (Jenkins et al., 1991) and 385 to 475 kg for bison cows (unpublished data, Ft. Niobrara Wildlife Refuge 1.

Carcass and Meat Characters. At 24 h postmortem carcasses were quartered between the 12th and 13th ribs, graded (USDA, 1976), and evaluated for ad- justed fat thickness, marbling, lean color, and texture. Both loins were removed from carcasses at 48 h postmortem. A 6-cm section was removed from the anterior end of all left loins. The section was used to obtain samples for fiber type characteristics. The remainder of the section, after removing all epimysium, was diced, frozen in liquid nitrogen, powdered, and subsequently analyzed for fat and moisture. A 6-cm section (longissimus muscle) from the anterior of all right loins was wrapped in polyvinyl chloride film and allowed to “bloom” for 3.5 h and evaluated for various color parameters including HunterLab “L” conducted on a Hunter Spectrophotom- eter (Model D54 P-5, HunterLab, 1983).

At 48 h postmortem, the 9-10-11 rib cut was removed from the left side and dissected into bone and soft tissue for chemical analysis of the soft tissue (Hankins and Howe, 1946). Fat and moisture analy- sis were conducted in duplicate on liquid N2 powdered samples of longissimus muscle and 9-10-11 rib soft tissue by ether extraction and oven drying, respec- tively (AOAC, 1975). Cholesterol content of the longissimus muscle and subcutaneous fat was deter- mined by the procedure of Rhee et al. ( 1982) modified for saponification.

Three samples for fiber-type characteristics were obtained from the 6-cm section from the anterior end of the left loins. Transverse sections of each muscle sample were cut 10 pm thick using a cryostat and stained for alkali-stable ATPase as described by Guth and Samaha ( 19 70). Serial sections were stained for succinate dehydrogenase activity according to proce- dures described by Troyer (1980). Sections were photographed by a photomicroscope and enlarged. Fibers were then counted and classified as white, red, or intermediate based on staining intensity. The area of 10 fibers of each type was then determined using a Bioquant particle-size analyzer. White, intermediate, and red fibers were expressed as percentages of total

BISON, BOS TAURUS, AND BOS x BISON TRAITS 1273

fiber numbers, their mean areas as square microme- ters, and total areas as percentages of total area. The remainder of the loins were vacuum-packaged and aged to 7 d postmortem and frozen. At a later date, loins were cut into 2.5-cm-thick steaks and used for shear and sensory evaluation.

Steaks for objective textural analyses were thawed, tempered, and cooked on Faberware Open Hearth broilers (Model 450N) to an internal temperature end point of 70°C. After cooking, steaks were wrapped and placed in a 2 to 3°C cooler. After 24 h, eight 13-mm cores per steak were taken parallel to fiber direction. Shear force was measured using an Instron 1132/Microcon I1 with a Warner-Bratzler shear at- tachment. Data included peak energy, load (shear force), and elongation, fail energy, load, and elonga- tion.

A taste panel was trained and tested according to methods described by AMSA ( 1978) and Cross et al. ( 1978). Ten panelists evaluated three samples from each loin for variation in juiciness, amount of connec- tive tissue, tenderness, flavor intensity, and off-flavor.

The right side was dissected into primal cuts 7 to 8 d postmortem according to Institutional Meat Pur- chase Specifications for Fresh Beef (USDA, 1975). Cuts were trimmed to an average of 8 mm of fat cover and boned out.

Experiment 2

Growth Characters. The second experiment in- volved 13 bison hybrids (Charolais x bison) and 17 animals from a composite population of BOS breeds (approximate proportions, .36 Simmental, .l8 Hereford, . l9 Holstein, . l0 Charolais, .09 Swedish Friesian, .04 Brown Swiss, .02 Angus, and .02 other breeds). All animals were castrated and dehorned. The bison hybrids were obtained from Wayne and Bob Jones, Huron, SD. Bison inheritance was verified by visual inspection and blood typing by Stormont Laboratories, Woodland, CA. The BOS animals were raised at the US. Meat Animal Research Center and were selected to match the initial weights of the bison hybrids. Animals were fed in three pens equipped with electronic headgates to measure individual feed in- take. Animals of each species type were divided into three weight groups, light (BOS, 156 to 230 kg; BHY, 162 to 223 kg), medium (BOS, 230 to 294 kg; BHY, 269 to 343 kg), and heavy (BOS, 368 to 444 kg; BHY, 365 to 447 kg), and assigned to pens by weight groups. Growth, feed intake, and digestibility data were collected. Animals were fed three diets with weight and feed intake evaluated each 21 d. The diets were 1) 100% bromegrass hay (ME, 2.1 Mcalkg) fed the first 63 d, 2) 66% corn silage, 22% corn, 12% protein-mineral supplement (ME, 2.69 Mcalkg), fed for 63 d after allowing 21 d for the changeover of diets 1 and 2; and 3) 38.5% corn silage, 56% corn, 5.5% protein-mineral supplement, (ME, 2.93 Mcalkg) fed for 63 d after 14 d for the changeover of diets 2 and 3.

All percentages are on a DM basis. Animals in the light weight pen were deemed too small to eat properly from the electronic headgates on the initial date and, therefore, were fed diet 2 until they began the experiment at period 2.

Digestion Triul. Fecal grab samples were collected from the rectum of all animals at 7-d intervals during each of the 21-d dietary periods following completion of diet changes. Composite feed samples were also collected for each 7-d period. Feed and fecal samples were analyzed for NDF, ADF, and ADL according to Goering and Van Soest (19701, CP (AOAC, 19751, GE by bomb calorimetry, DM, and AIA (Van Keulen and Young, 1977). Hemicellulose (NDF - ADF) and cellulose (ADF - ADL) concentrations were estimated from the detergent fiber data. In vivo digestion coefficients were calculated for DM, CP, GE, NDF, hemicellulose, and cellulose using AIA as an internal marker for each animal a t each sampling data. Mean digestion coefficients were calculated for each animal on each diet for use in the statistical analysis.

Carcass and Meat Characters. Animals were con- tinued on diet 3 for 224, 301, 378, or 545 d until animals reached the appropriate weight end points and were slaughtered. The BOS were slaughtered when they reached approximately 545 kg and BHY when they averaged approximately 490 kg. Carcass and meat data were collected following procedures outlined for Exp. 1.

Experiment 3

Growth Characters. The third experiment involved 4 bison, 7 bison hybrids, and 10 composite BOS animals similar to those used in Exp. 2. The bison hybrids (Charolais x bison) were obtained from Bob Jones, Huron, SD. The BOS were selected to generally match the range of weights of the bison hybrids. All animals were fed in pens equipped with electronic headgates to measure individual feed intake, each species housed in separate pens. Growth evaluation covered four 84-d periods (336 d) with weight and feed intake evaluated at 28-d intervals. Beginning April 8, three diets were fed with changeover of diets accomplished during the 1st wk of each 84-d period. Periods and diets on a DM basis were 1) alfalfa hay (ME, 2.1 Mcalkg), 2) 75% alfalfa hay and 25% corn (ME, 2.39 Mcalkg), and 3 ) 50% alfalfa hay and 50% corn (ME, 2.68 Mcalkg), Diet 3 was also fed throughout period 4.

Digestion Trial. Three weekly feed and fecal samples were collected after 28 d of feeding each diet. The protocol was the same as in Exp. 2 except that fecal samples were collected immediately after defeca- tion rather than as rectal grab samples. Animals were observed over 2 d to collect individual fecal samples from each animal during each sampling week. Chemi- cal analyses and calculation of digestion coefficients were the same as in Exp. 2, except that internal marker concentrations for each animal were averaged over the three weekly collections before calculating the

1274 KOCH ET AL.

Table 1. Experiment 1, weight, dry matter intake, daily gain, and gain efficiency for two 112-day periods

Item and period BOSa BISa SEDa

Initial wt, kg 249.4 184.9 27.4 End wt, kg 1 375.0 252.9 43.7 2 503.3 357.2* 46.0

DMI, kg/d 1 8.51 5.25? .91 2 11.09 7.16? 1.49 Avg 9.80 6.34* .87

1 2.72 2.52** .01 2 2.52 2.32A .19 Avg 2.62 2.42' .os

1 1.12 .60' .16 2 1.14 .93 .13 Avg 1.13 .77* .10

1 131.5 109.0 9.0 2 103.0 134.5 22.4

12.1

DMI, % of BW

ADG, kg/d

ADGDMI, &g

Avg 117.2 121.8 aBOS = Bos taurus; BIS = bison, SED = average standard error of difference. +P < .lo, BOS = BIS. *P < .05, BOS = BIS. **P < .01, BOS = BIS.

Table 2. Experiment 2, weight, dry matter intake, daily gain, and gain efficiency on three diets

Item and PDa BOSb BHYb SED^ Initial wt, kg 293.4 301.2 34.4 End wt, kg 1 327.4 323.0 30.3 2 406.2 393.0 30.2 3 494.4 434.3* 30.4

1 7.46 6.46** .32 2 9.78 8.25** .58 3 10.07 6.31** .42

Avg 9.11 7.01** .26

DMI, kg/d

DMI, % of BW 1 2.15 1.87** .077 2 2.65 2.30** ,083 3 2.18 1.51** ,061 Avg 2.33 1.89** ,044

1 .37 .23** .099 2 1.37 1.24* .095 3 1.14 .53** .092 Avg .96 .67** .056

1 50.8 34.2* 13.4 2 151.7 156.2 12.0 3 115.5 79.4** 10.4 -4% 106.0 89.9* 6.9

ADG, kg

ADGDMI, g k g

aPeriod-diet: 1 = smooth bromegrass; 2 = 66% corn silage, 22% corn, 12% protein-mineral supplement; 3

bBOS = Bos taurus; BHY = BOS x bison; SED = average standard error of difference. *P < .05, BOS = BHY. **P < .01, BOS = BHY.

= 38.5% corn silage, 56% corn, 5.5% protein-mineral supplement.

BISON, BOS TAURUS, AND BOS x BISON TRAITS 1275

digestion coefficients. This resulted in a lower error mean square than in Exp. 2.

After the 336-d feeding trial animals were fed a diet of 25% alfalfa hay, 71.4% corn, and 3.16% urea (ME, 2.95 Mcalkg) until they reached approximate target slaughter weights after 376 or 496 d on feed. Carcass and meat were collected following the procedures outlined for Exp. 1.

Analysis of Data. Statistical analyses of variance were conducted using the GLM procedures of SAS (1989). Because we were not always able to obtain animals of each species type that matched in age and weight at the beginning of each experiment, differ- ences in weight may bias some comparisons. However, variation in rate of gain is an inevitable cause of weight differences that can affect comparisons of feed intake or efficiency but are characteristics of the populations evaluated.

The analytical model for growth data in Exp. 1 included the fixed effects of species, period, and species x period, with pens as the experimental units. In Exp. 2, the model included the fixed effects of species, 21-d weigh interval, and species x weigh

interval. Data were analyzed separately by diets. In Exp. 3, data were analyzed separately by 84-d periods with species, 28-d weigh interval, and species x weigh interval as fixed effects. Because of individual feeding records in Exp. 2 and 3, animals were treated as the experimental units. The models for digestibility ana- lyses included fixed effects of diet, species, and the diet x species interaction. Carcass data were analyzed separately for pairs of experiments with animals as the experimental units and species contrasts of BOS with BIS ( 1 and 3 ) or of BOS with BHY (2 and 3) and experiment as fixed effects. The estimates of these differences were added to the least squares means of BOS over all experiments to derive means for BHY or BIS.

Results and Discussion

Feed Intake, Growth, and Efficiency of Gain

Experiment 1. Results from the growth evaluation phase are shown in Table 1. Initial weights of BIS

Table 3. Experiment 3, weight, dry matter intake, daily gain, and gain efficiency on three diets

Item and PDa BOSb BHYb B I S ~ SEDb

Initial wt, kg 283.5 272.7 248.St 17.2 End wt, kg 1 346.1 327.4 249.0** 19.3

3 473.4 414.2** 354.7** 21.2 4 470.4 457.7 382.2** 23.9

1 7.54 7.34 4.90** .61 2 9.15 7.95* 6.31** .62 3 11.58 8.51** 7.64** .63 4 8.29 7.25 7 .OS .62 Avg 9.14 7.75** 6.46** .3 1

2 405.4 364.gt 297.3** 22.7

DMI, kgid

DMI, % of BW 1 2.36 2.46 1.93 .l8 2 2.49 2.32 2.24 . l6 3 2.60 2.18** 2.42 . l5 4 1.79 1.67 2.05 . l3 Avg 2.31 2.16" 2.16? .08

ADG, kgld 1 .75 .65 .004** . l0 2 .71 .45* .57 .l1 3 .S1 .59* .68 . l 4 4 -.01 .53** .53** . l5 Avg .56 .55 .45' .06

ADGDMI, g/kg 1 111.6 92.1 -22.7"" 21.0 2 70.5 56.6 81.2 18.3 3 69.6 72.6 88.5 11.7 4 -1.8 68.1** 58.7** 20.4 A T 62.5 72.3 51.4 9.1

aPeriod-diet: 1 = alfalfa hay, 2 = 75% alfalfa, 25% corn, 3 and 4 = 50% alfalfa, 50% corn. bBOS = Bos tuurus; BHY = BOS x bison; BIS = bison; SED = average standard error of difference. TP < .lo, BOS = BHY, BIS. *P < .05, BOS = BHY, BIS. **P < .01, BOS = BHY, BIS.

1276 KOCH

were 64 kg less than those of BOS and the difference increased to 146 kg for the final weight. The DM1 of BOS exceeded that of BIS, and DMI/BW tended to be higher for BOS. Bison gained less per day than BOS, but BIS gains improved in period 2, which could be due to increased adaptation to the confinement situation of pen feeding. Efficiency of gain (ADG/ DMI) was higher for BOS than for BIS in the first period but was reversed for the second 112-d period. The difference between species for the 224-d period was not significant.

Experiment 2. Growth characteristics are shown in Table 2. Initial weights of each species type were similar. The BHY animals, though more nervous than BOS, seemed to adapt reasonably well to the confine- ment feeding system. The BOS gained significantly more than BHY in each period. Feed intake of BHY was less than that of BOS during the experiment and BHY consumed significantly less feed per unit of weight. Gain efficiency, ADGDMI, was higher for BOS than for BHY during periods 1 and 3 and for the average.

Variation of average daily gain and feed consump- tion of individual animals for the three 21-d intervals of each diet period following changeover of diets was examined to aid in interpreting the changes in DM1 and ADG of BOS and BHY, particularly for period 3

ET AL.

(Table 2). In period 1, BOS had slightly more variation in DM1 with a higher CV than BHY, but ADG was more variable for BHY. Both species lost weight during the second 21-d interval. In period 2, the CV of DM1 and ADG were similar for BOS and BHY, 15.5 vs 15.8%. In period 3, DM1 and ADG declined in each subsequent 21-d interval for both BOS and BHY, but the decline was greater in BHY. The CV of DM1 was greater for BHY than for BOS, 23.9 vs 12.796, and the variation in DM1 was not influenced by just one or two extreme animals. The feeding trial began on February 19. Periods 1, 2, and 3 ended on April 2, July 15, and September 30, respectively. The average minimum and maximum temperatures ( "C) for the three periods were 1) -.9 and 13.0, 2 ) 15.1 and 27.4, and 3 ) 14.7 and 25.6, respectively. Temperatures during periods 2 and 3 were not greatly different. Selection during domestica- tion of BOS for increased growth rate and feed consumption may be the important factor.

Experiment 3. Growth characteristics are given in Table 3. The BOS had larger initial weights and, except for period 4, gained more per day and tended to consume more feed per unit of body weight with a higher DM1 per day than BIS or BHY, although differences were not always significant. Gain eff- ciency, ADGDMI, tended to be higher for BIS than for BOS, except for period 1, in which weight loss by two

Table 4. Experiment 2, analysis of variance and least squares means of digestion coefficients for three dietsa

Source df DM CP GE NDF HCb C E L ~

F-statistics and error mean square Diet 2 110.1** 81.5** 101.3** 7.5** 16.5** 1.5 Species 1 10.9** 6.3** 8.3** 3.2t 3.1t 3.1t Diet x species 2 .8 1.4 1.2 .4 .3 .4 Error 72 59.9 67.4 67.4 99.9 100.2 123.7

Least squares means and probability BOS = BHY by diets Diet 1 BOSC 40.8 38.8 41.0 43.7 48.8 50.4 BHYC 43.6 39.1' 42.2 46.0 51.0 53.5 SEDC 3.5 3.7 3.7 4.5 4.5 5.0

BOS 61.6 62.6 62.3 52.9 57.2 56.2 BHY 68.7* 68.6** 69.3* 56.3 60.7 59.0 SED 2.9 3.3 3.2 3.8 3.8 4.2

BOS 71.2 63.5 71.0 51.8 63.3 50.8,

SED 2.8 3.1 3.0 3.7 3.7 4.1

BOS 57.8 55.0 58.1 49.5 56.4 52.4

SED 1.8 1.9 1.9 2.3 2.3 2.6

Diet 2

Diet 3

BHY 79.2** 71.8** 79.5** 58.7' 69At 58.4'

Avg

BHY 63.8** 59.9** 63.6** 53.6? 60.5+ 57.0t

aDiets: 1 = smooth bromegrass: 2 = 66% corn silage, 22% corn, 129% protein-mineral supplement; 3 = 38.5% corn silage, 56%' corn, 5.5%

bHC = hemicellulose; CEL = cellulose. CBOS = Bos taurus; BHY = BOS x bison; SED = average standard error of difference.

*P < .05. **P < .01.

protein-mineral supplement.

tP < .lo.

BISON, BOS TAURUS, AND BOS x BISON TRAITS 1277

of the BIS markedly affected the results. Period 4 included some extremely cold temperatures that affected feed intake and gains of all animals, but particularly those of BOS. The average minimum and maximum temperatures ( "C ) for the four periods were 1) 11.8 and 25.5, 2) 15.3 and 28.2, 3 ) 0 and 13.7, and 4) -10.4 and 2.1. Christopherson et al. (1976) reported that BIS calves had a lower metabolic rate, especially a t low temperatures, than did Hereford and Scottish Highlander, Bos taurus breeds.

Growth contrasts in these data should be inter- preted with caution. Although a long adjustment period was used before starting the experiments, confinement to pens and intake of a diet with moderate or high density are abnormal for bison. They are not domesticated animals.

When all three experiments are considered, we conclude that BOS consumed more feed and gained more per day than BIS or BHY, but efficiency of gain did not differ among species. Including live weight as a covariate did not change the conclusions. There was no tendency for BIS or BHY to gain more than BOS on the higher-roughage diets (i.e., diet 1 in Tables 2 and 3 1. Peters ( 1958 reported that bison hybrids made greater gains than bison and lower gains than Herefords. Bison were reported to be less efficient

than hybrids or Herefords in feed conversion through a time-constant feeding period on a diet of approxi- mately 25% grass-alfalfa hay, 50% ground barley, and 25% ground oats.

Digestibility of Diets by Species

Experiment 2. Analysis of digestion coefficients of three diets by BOS and BHY are presented in Table 4. Diet components included DM, CP, GE, NDF, hemicel- lulose ( HC), and cellulose ( CEL). Digestion coeffi- cients tended to increase as the level of corn in the diet increased. Bison hybrids had higher digestion coeffi- cients for all components and for all diets, but differences were not always significant. The species x diet interactions were not significant for any compo- nent; however, differences tended to be greater at higher levels of corn in the diet.

Experiment 3. Analysis of digestion coefficients of three diets differing in percentage of alfalfa hay and corn by BOS, BHY, and BIS is presented in Table 5. As in Exp. 2, average digestibility of diets tended to increase as percentage of corn increased, except for NDF and CEL. The BOS had lower digestion coeffi- cients than BHY or BIS for each component. Differ- ences between BOS and BHY or BIS tended to be

Table 5. Experiment 3, analysis of variance and least squares means of digestion coefficients for three dietsa

Source df DM CP GE NDF HCb C E L ~

Diet Species Diet x species Error

Diet 1 BOSC BHYC BISC SEDC

Diet 2 BOS BHY BIS SED

Diet 3 BOS BHY BIS SED

BOS BHY BIS SED

Avg

F-statistics and error mean square 2 20.8** 42.8** 21.1** 12.6** 20.0** 30.1** 2 11.2** 7.6** 9.3** 10.7** 4.7** 10.1** 4 1.9 3,6** 1.8 .3 .3 . l

59 17.8 14.1 21.6 42.8 49.6 34.2 Least squares means and probability BOS = BHY, BIS

59.5 61.1 57.5 56.2 48.8 67.4 67.2** 65.4* 64.8"" 64.5** 54.51 74.4" 70.1** 71.7** 68.2** 66.2** 57.2* 74.9* 2.2 1.9 2.4 3.3 3.6 3.0

66.5 74.8 64.4 60.4 60.4 55.0 70.1t 76.4 67.8 65.6* 65.6 61.3* 69.3 76.2 67.1 65.2 65.2 59.5 2.2 1.9 2.4 3.3 3.6 3.0

72.2 73.6 70.8 52.3 63.9 63.9 75.4 76.1 74.1 60.2* 69.2 71.0" 74.6 74.5 73.1 58.2t 66.5 69.2+ 2.2 2.0 2.4 3.4 3.7 3.0

66.2 69.8 64.2 52.2 57.8 62.1 70.9** 72.6** 68.9** 59.9** 63.1** 68.9** 71.3** 74.1** 69.5** 59.3** 63.0* 67.9**

1.2 1.1 1.4 1.9 2.1 1.7

1278 KOCH ET AL

Figure 1. Bos taurus.

larger for diet 1 than for diets 2 and 3. However, species x diet interactions were significant only for CP where BIS and BHY were significantly higher than BOS for diet 1 but not for diets 2 and 3.

Results from both experiments indicate that BIS and BHY had higher digestion coefflcients than BOS. The higher digestibility by BIS and the hybrids could have been influenced by their lower rate of DM1 with a resulting longer retention time for digestion. Schaefer et al. ( 1978) reported longer digesta reten- tion times for bison than for Holstein or Hereford cattle fed a mixed grass-legume hay at equal intake levels. However, our conclusions were not altered when DMI/BW was used as a covariate in the analyses. Richmond et al. (1977) and Hawley et al. ( 198 1) also reported higher digestibility of forages for bison than for cattle. Lack of species x diet interac- tions for most of the components indicates that higher

Figure 2. Bison bison.

digestibility for bison could be general in nature and not restricted to high- vs low-roughage diets.

Carcass Characteristics of Species

Composition of the side and cuts as a percentage of side weight are shown in Table 6. Bison had more trimmed boneless retail product ( a s a percentage of side weight) and less fat trim and bone than BOS in all cuts except for fat trim in the rib cut. Part of the difference in chuck retail product was associated with the long dorsal spinous processes of BIS relative to BOS. The higher percentage of fat trim in the rib cut of BIS may have evolved as a storage depot for energy or as protection from a cold environment. The relative proportion of the total fat trim (including kidney fat) indicated that BIS had 4.7, 9.8, and 5.4% more of their fat in the chuck, rib, and kidney knob, respectively, than BOS. This was matched by -3.0, -7.0, and -9.9% less of their fat trim in the loin, round, and minor cuts. Bison hybrids tended to be intermediate to BIS and BOS. Figures 1 and 2 illustrate the differences in distribution of external fat cover for the two species.

BISON, BOS TA URUS, AND BOS x BISON TRAITS 1279

The BOS have a much more uniform fat cover over the carcass than BIS, and fat cover down to the brisket is much thicker for BOS than for BIS. Note that in BIS the fat cover high on the exposed rib surface is as great or greater than that in BOS, but it decreases rapidly down toward the brisket. The proportion of total weight of retail product (lean plus 8 mm of fat cover) in cuts indicated that BIS carry more of their muscling in the chuck (2 .6%) and rib ( .4%) and less in the loin (-.g%), round (- .6%), and minor cuts (-1.5%). Although these are small differences in distribution they were statistically significant. Thus, there was no evidence that the extra rib of BIS, which would be included in the full loin, resulted in an increase of relative muscle mass in the loin cut, largely because of the extra amount of retail product associated with the chuck and rib.

Additional carcass characteristics are presented in Table 7. The BOS were slaughtered when they reached weights in the range of 480 t o 600 kg after continuing on feed following the growth studies discussed earlier. Bison were continued on feed until they reached weights in the range of 370 to 495 kg. Lower slaughter weights of bison was an attempt to compare carcass characteristics at a similar maturity. Bison hybrid animals were slaughtered at weights

intermediate to those of BOS and BIS. Although BIS and BHY animals were slaughtered at lighter weights, they required 58 and 28 more days, respectively, to reach target weights. Bison and BHY had higher dressing percentages, 1.9 and 3.6%, and a lower proportion of their carcass weight in the hindquarter, -2.6 and -1.3576, respectively, than BOS. Peters ( 1958) and Hawley ( 1986) also reported Bison had less of their carcass weight in the hindquarter. The long spinous processes in the thoracic region make the hindquarter seem much smaller than the forequarter. However, the depth of muscle in this area of BIS is less than that of domestic cattle, so the proportion of hindquarter is not as small as it seems to be.

The fat thickness of BIS and BHY was higher than that of BOS even though their total fat trim was lower and was associated with the location of measurement at the 12th rib. This is illustrated in Figures 1 and 2, which show the lack of fat cover in all but the chuck and rib cuts of bison. Intramuscular fat as measured by marbling score and chemical fat in the longissimus muscle was lower in BIS than in BOS.

Shear force, overall sensory tenderness, and amount of connective tissue scores indicate that BIS were more tender and BHY were less tender than BOS. Perceived juiciness was higher in BIS than in

Table 6. Side weight and cut composition (trimmed retail cut, fat trim, and bone) as a percentage of side weight

Item BOSa BHYa BISa SEDa

Side wt, kg 155.8 149.5+ 126.2** 4.24 Retail 65.9 69.1** 71.9** .72 Fat trim 16.4 15.5 12.2** .97 Bone 17.7 15.4** 15.9** .47

Chuck 27.2 29.0** 30.5** .31 Retail 19.8 21.7** 23.4** .30 Fat trim 2.8 2.8 2.6 . l 8 Bone 4.6 4.4+ 4.5 . l 4

Rib 8.1 8.0 9.7** .27 Retail 5.2 5.4 6.0** . l 8 Fat trim 1.2 1.3 2.1** . l 4 Bone 1.7 1.3** 1.6* .07

Loin 14.8 14.3* 13.7* . l 7 Retail 10.4 10.5 10.7* . l 6 Fat trim 2.1 1.8+ 1.0** . l 6 Bone 2.3 2.0** 2.1** .07

Round 25.2 23.9** 24.3** .37 Retail 18.4 18.6 19.6** .35 Fat trim 2.1 1.4** .7** . l 3 Bone 4.7 3.9** 4.1** . l 4

Minor cutsb 21.9 21.5 m a * * .37 Retail 12.2 12.8* 12.3 .24 Fat trim 5.4 4.9 2.2** .36 Bone 4.3 3.8** 3.2** . l 4

Kidney knob 2.8 3.3t 3.0 .21

aBOS = Bos tuurus; BHY = BOS x bison; BIS = bison; SED = average standard error of difference. bMinor cuts: foreshank, short plate, brisket, and flank. ' P < .lo, BOS = BHY, BIS. *P < .05, BOS = BHY, BIS. **P < .01, BOS = BHY, BIS.

1280 KOCH ET AL.

Table 7. Carcass and meat characters

Character BOSa BHYa BISa SEDa

Initial wt, kg Slaughter wt, kg Days to slaughter Hot carcass wt, kg Dressing percent Hindquarter, %

Fat thickness, mm Fat, 9-10-11 rib, % Longissimus fat, % Marblingb Shear peak, kg Tendernessb Connective tissue’ Juicinessb Flavor intensityb off-flavor’ Cholesterol, mg/100g M. longissimus Subcutaneous fat

Lean colorb Hunter L colorb Textureb Muscle fibers, LT0 White Intermediate Red White area Intermediate area Red area

275.4 541.8 319.0 326.6 60.7 49.0

8.2 29.6 4.1

386.0 5.1 5.1 5.0 5.1 4.5 2.7

54.8 100.8

5.3 22.9

6.0

45.0 26.9 28.0 57.8 21.0 21.1

280.9 485.2** 347.0 309.8* 64.3** 47.7** 10.2+ 29.8 4.0

449.0* 5.5 4.6* 4.4* 5.0 4.2* 2.5*

59.4** 88.3* 5.1

22.1 6.4

39.6** 28.5 32.1** 52.8* 22.6 24.6*

221.1* 431.3** 377.0** 269.0**

62.6** 46.4** 22.1** 33.8*

2.9* 319.0%

4.7 5.7* 5.6* 5.4** 3.7** 2.1**

58.0 96.7 4.4*

17.6** 6.2

40.0** 33.3** 26.7 56.6 25.6** 17.9*

17.2 12.7 24.4 8.7

.67

.27

. l 4

.46 2.1

28.1 .52 .24 .23 . l 6 . l 4 . l0

2.2 5.1

.42 1.76 .36

1.6 1.7 1.3 2.2 1.7 1.4

aBOS = Bos taurus; BHY = BOS x bison; BIS = bison; SED = average standard error of difference. bScores: marbling, 100 to 199 = practically devoid, 900 to 999 = abundant; tenderness, 1 = tough, 8 =

tender; connective tissue, 1 = abundant, 8 = none; juiciness, 1 = dry, 8 =juicy; flavor intensity, 1 =bland, 8 = intense; off flavor, 1 =intense, 4 = none; Color, 1 = dark, 8 = light; Hunter L color, 0 = black, 100 = white; texture, 1 = coarse, 8 = fine.

‘P < .lo, BOS = BHY, B E . *P < .05, BOS = BHY, BIS. **P < .01, BOS = BHY, BIS.

BOS even though they had less intramuscular fat. Beef flavor intensity was less than BOS. The sensory panel identified a noticeable “off-flavor” in BIS, which they described as a more intense ammonia, metallic, and gamey flavor (Larick et al., 1989).

Cholesterol, a necessary component of every animal cell, was measured in the longissimus muscle and in subcutaneous fat of the rib cut. Bison and BHY had more cholesterol in the longissimus muscle but less in subcutaneous fat than BOS. This discrepancy among results for muscle and fat may be related to species differences of tissue composition. Larick et al. (1989) studied samples of meat from Exp. 1 and observed differences in the unsaturated and polyunsaturated fatty acid composition of Bison and BOS. Higher concentration of cholesterol has been reported in subcutaneous fat than in longissimus muscle by Eichhorn et al. (1986) and Wheeler et al. (19871, but these authors did not find differences between the BOS breeds that they studied. Rhee et al. ( 1982) reported that in uncooked muscle of cattle, only steaks of the marbling score “practically devoid had signifi-

cantly less cholesterol than steaks with any other marbling score.

Color differences of the longissimus muscle face were measured subjectively by scores and objectively by Hunter colorimeters (HunterLab, 1983). Muscle from BIS and BHY was darker than that from BOS but did not differ significantly in texture.

Muscle fiber type differed significantly between species. Bison had a lower percentage of white and a higher percentage of intermediate fibers than BOS with essentially no difference in percentage of red fibers. The area occupied by these types followed the same pattern, but the relative differences decreased for white and increased for red fibers. Bison hybrids had a lower percentage of white but a higher percentage of red fibers than BOS. The darker color of BIS relative to BOS does not seem to be consistent with the pattern of fiber types and areas. However, color differences are also influenced by pigment concentration and pH in muscles. It is possible that these differences in fiber percentage patterns of BIS and BHY may explain the discrepancies of shear force

BISON, BOS

and sensory perception of tenderness and connective tissue for BHY and BIS.

TA URUS, AND BOS x BISON TRAITS

amount of

Implications

Bos tuurus gain more rapidly than bison and bison hybrids except during periods of extremely cold weather. The slightly higher digestion coefficients for Bison than for Bos taurus offers interesting possibili- ties as an investigative model or for gene introduction into cattle populations. The decreased amount of carcass fat in bison while maintaining as good or better tenderness scores than Bos tuurus seems worthy of further study. Because of problems of temperament and market development, bison will likely contribute primarily to niche production and market situations, and as a tool for further research.

Literature Cited

AMSA. 1978. Guidelines for cookery and sensory evaluation of meat. Am. Meat Sci. Assoc., National Live Stock and Meat Board, Chicago, IL.

AOAC. 1975. Official Methods of Analysis (12th Ed.). Association of Offcial Analytical Chemists, Washington, DC.

Boyd, M. M. 1908. A short account of an experiment in crossing the American Bison with domestic cattle. Am. Breeders Assoc. Annu. Rep. 4:324.

Boyd, M. M. 1914. Crossing bison and cattle. J. Hered. 5:189. Christopherson, R. J., R. J. Hudson, and R. J. Richmond. 1976. Feed

intake, metabolism, and thermal insulation of Bison, Yak, Scot- tish Highlander, and Hereford calves during winter. Univ. of Alberta Agric. Bull., 55th Feeders Day Rep. pp 49-52.

Cross, H. R., R. Moen, and M. S. Stanfield. 1978. Training and testing of judges for sensory analysis of meat quality. Food Technol. 32:48.

Deakin, A., G. W. Muir, and A. G. Smith. 1935. Hybridization of domestic cattle, bison and yak. Can. Dept. Agric. Publ. 479, Tech. Bull. 2.

Eichhorn, J. M., E. J. Wakayama, G. J. Blomquist, and C. M. Bailey. 1986. Cholesterol content of muscle and adipose tissue from crossbred bulls and steers. Meat Sci. 16:71.

Goering, H. K., and P. J. Van Soest. 1970. Forage fiber analyses (apparatus, reagents, procedures, and some applications). Agric. Handbook No. 379. ARS USDA, Washington, DC.

Goodnight, C. 1914. My experience with bison hybrids. J. Hered. 5: 197.

Guth, L., and F. J. Samaha. 1970. Procedure for the histochemical demonstration of actomyosin ATPase. Exp. Neurol. 28:365.

Hankins, 0. G., and P. E. Howe. 1946. Estimation of the composition of beef carcasses and cuts. USDA Tech. Bull. 926, Washington, DC.

Hawley, A.W.L. 1986. Carcass characteristics of Bison (Bison bison) steers. Can. J. Anim. Sci. 66:293.

1281

Hawley, A.W.L., D. G. Peden, and W. R. Stricklin. 1981. Bison and Hereford steer digestion of sedge hay. Can. J. Anim. Sci. 61: 165.

HunterLab. 1983. The science and technology of appearance meas- urement. Hunter Associates Laboratory, Reston, VA.

Jenkins, T. G., M. Kaps, L. V. Cundiff, and C. L. Ferrell. 1991. Evaluation of between- and within-breed variation of weight- age relationships. J . h i m . Sci. 69:3118.

Jones, C. J. 1907. Breeding catalo. Am. Breeders Assoc. Annu. Rep. 3:161.

Koch, R. M,, J. D. Crouse, and S. C. Seideman. 1988. Bison, Hereford, and Brahman growth and carcass characteristics. Beef Research Progress Rep. No. 3. ARS-71. p 26. ARS, USDA, Washington, DC.

Koch, R. M,, M. E. Dikeman, D. M. Allen, M. May, J. D. Crouse, and D. R. Campion. 1976. Characterization of biological types of cattle. 111. Carcass composition, quality and palatability. J . h i m . Sci. 43:48.

Koch, R. M,, M. E. Dikeman, R. J. Lipsey, D. M. Allen, and J. D. Crouse. 1979. Characterization of biological types of cattle-cycle 11. 111. Carcass composition, quality and palatability. J. Anim. Sci. 49:448.

Koch, R. M,, M. E. Dikeman, and J . D. Crouse. 1982. Characteriza- tion of biological types of cattle (cycle 111): 111. Carcass compo- sition, quality and palatability. J . h i m . Sci. 54:35.

Larick, D. K., B. E. Turner, R. M. Koch, and J. D. Crouse. 1989. Influence of phospholipid content and fatty acid composition of individual phospholipids in muscle from Bison, Hereford and Brahman steers on flavor. J. Food Sci. 54:521.

Logan, V. S., and P. E. Sylvestre. 1950. Hybridization of domestic beef cattle and buffalo. Progress Rep. 1937-1949, Anim. Husb. Div., Can. Dept. Agric.

Peters, H. F. 1958. A feedlot study of bison, cattlo and Hereford calves. Can. J. Anim. Sci. 38:87.

Rhee, K. S., T. R. Dutson, G. C. Smith, R. L. Hostetler, and R. Reiser. 1982. Cholesterol content of raw and cooked beef longis- simus muscles with different degrees of marbling. J. Food Sci. 47:716.

Richmond, R. J., R. J. Hudson, and R. J. Christopherson. 1977. Comparison of forage intake and digestibility by American bison, yak and cattle. Acta Theriol. 22:225.

SAS. 1989. SAWSTAT@ User’s Guide (Version 6, 4th Ed.). SAS Inst. Inc., Cary, NC.

Schaefer, A. L., B. A. Young, and A. M. Chimwano. 1978. Ration digestion and retention times of digesta in domestic cattle ( Bos taurus), American bison ( Bison bison), and Tibetan yak ( Bos grunniens). Can. J. Anim. Sci. 56:2355.

Troyer, H. 1980. Oxidoreductases. In: Principles and Techniques of Histochemistry. pp 299-300. Little, Brown and Co., Boston, MA.

USDA. 1975. Institutional Meat Purchases Specifications for Fresh Beef. Agric. Marketing Serv., USDA, Washington, DC.

USDA. 1976. Official United States standards for grades of carcass beef. Title 7, Ch. 28, Pt. 2853, Sections 102-107. Code of Federal Regulations, USDA, Washington, DC.

Van Keulen, J., and B. A. Young. 1977. Evaluation of acid-insoluble ash as a natural marker in ruminant digestibility studies. J. Anim. Sci. 44:282.

Wheeler, T. L., G. W. Davis, B. J. Stoecker, and C. J . Harmon. 1987. Cholesterol concentration of longissimus muscle, subcutaneous fat and serum of two beef cattle breed types. J. Anim. Sci. 65: 1531.