AMERICAN BISON, Bison bison L.

S.E. Knapp, T.J. DeLiberto, S.M. Button & M.C. Rognlie

Veterinary Molecular Biology Laboratory

Montana State University-Bozeman

Bozeman, Montana

Copyright C 1996


  1. Ben Shaul, D.M. 1962. The composition of the milk of wild animals. International Zoo Yearbook. 4: 333-342.

    ABSTRACT: Not available

  2. Christopherson, R.J., R.J. Hudson & R.J. Richmond. 1976. Feed intake, metabolism and thermal insulation of bison, yak, Scottish Highland and hereford calves during winter. 55th Annual Feeder's Day Report. 55: 51-52.

    ABSTRACT: Bison, yak and Scottish Highland cattle have relatively thick and dense hair coats and for this reason are considered to be extremely cold tolerant. However, there is no quantitative data on the thermal insulations and metabolic responses of these animals during cold exposure. The objectives of the present study were to compare the metabolic rates, thermal insulations and lower critical temperatures of bison, yak, Scottish Highland and Hereford calves during winter.
    Insulation values for all calves were highest in January and February and showed a decline in March, likely as a result of hair shedding. The lower critical temperatures indicate the relative resistance of the calves to direct cold stress. The calves were ranked in order of increasing cold resistance as follows; Hereford < Yak < Highland < Bison.

  3. Christopherson, R.J., R.J. Hudson & R.J. Richmond. 1978. Comparative winter bioenergetics of American bison, yak, Scottish Highland and Hereford calves. Acta Theriologica. 23: 49-54.

    ABSTRACT: American bison, yak, Scottish Highland and Hereford calves were used in a comparative study of metabolic responses to temperature of 20, 0 and -30 degrees Celsius. Metabolic rates were lowest in the bison , highest in the Herefords and intermediate in the Highland and yak. Critical temperatures and thermal insulations as calculated from metabolic responses to three ambient temperatures suggested that the bison were most tolerant to cold and that the Herefords were least tolerant. Highland and yak were intermediate and comparable in this regard.

  4. Christopherson, R.J. & R.J. Hudson. 1978. Effects of temperature and wind on cattle and bison. 57th Annual Feeder's Day Report. 57: 40-41.

    ABSTRACT: In a previous study of the responses of animals to cold environments, bison were observed to reduce metabolic rates as the temperature fell as low as -30 degrees Celsius. This was in contrast to yak and cattle which showed an increased metabolic rate in response to cold below critical temperatures of about -15 degrees Celsius. The present study was conducted to determine whether bison and cattle differed in their response to cold throughout the year whether an increased metabolic rate could be elicited in bison by superimposing the effects of low temperatures and wind.
    Bison exhibited marked adaptations and tolerence to cold. They were as tolerent to cold at six months of age as cattle were at thirteen to seventeen months. Over a wide range of temperatures, metabolic rate of the bison decreased in response to low ambient temperatures whereas Herefords less than one year of age increased metabolic rates at -30 degrees Celsius to maintain body temperature. However, in very severe thermal environments, where both low temperatures and wind were superimposed, bison express a thermoregulatory increase in metabolic rate similar to the response shown by cattle.

  5. Christopherson, R.J., R.J. Hudson & M.K. Christopherson. 1979. Seasonal energy expenditures and thermoregulatory response of bison and cattle. Can. J. Anim. Sci. 59: 611-617.

    ABSTRACT: The metabolic rates of two bison and four Hereford spring-born calves were measured at monthly intervals from December until the following November. Following adaptation at seasonal ambient temperatures, metabolic measurements were made while calves were exposed to controlled temperatures of +10, 0 and -30 degrees Celsius. Exposure of the Hereford calves to -30 degrees Celsius resulted in increased metabolic rates during the first 6 months of the study but the magnitude of the response was greatly attenuated as the calves grew larger. At -30 degrees Celsius, bison calves either maintained or reduced metabolic rates compared to expenditures at +10 degrees Celsius. When the calves were about 17 months of age, they were exposed to a combination of low temperatures and wind. Wind velocities of 4.7 km/h did not influence metabolic rates of either bison or Herefords at air temperatures of 0 degrees Celsius. However, at -30 degrees Celsius, metabolic rates increased from 650 and 700 KJ kg-.75/d to 835 and 950 KJ kg-.75/d in Hereford and bison calves, respectively. Neither respiratory frequencies nor heart rates were influenced significantly during cold exposure, but heart rates increased with response to wind. In general, metabolic rates and heart rates were lower in bison calves.

  6. Dearden, B.L., R.E. Pegau & R.M. Hansen. 1975. Precision of microhistological estimates of ruminant food habits. Journal of Wildlife Management. 39: 402-407.

    ABSTRACT: Correction terms applied to the relative densities with which food fragments appear on microscope slides improve the estimate of dry weight of ingested foods as determined from microhistological analysis. Correction terms can be applied to undigested materials, fragments within rumen contents and fecal pellets, and to residues within nylon bags. The technique has been applied successfully to reindeer (Rangifer tarandus), cattle, and bison (Bison bison).

  7. Delgiudice, G.D., F.J. Singer, U.S. Seal & G. Bowser. 1994. Physiological reponses of Yellowstone wildlife to winter. J. Wildl. Manage. 58: 24-34.

    ABSTRACT: Because nutrition is critically related to other aspects of bison (Bison bison) ecology, and the winter ranges inhabited by bison in Yellowstone Park (YNP) are ecologically diverse, it was important to determine if nutritional deprivation differences occurred among winter ranges. We used chemistry profiles of urine suspended in snow to compare nutritional deprivation of bison from January to April 1988 on 4 sampling areas of 3 winter ranges in YNP. Declining (P < 0.001) trends of urinary potassium: creatinine ratios in bison on all 4 sampling areas indicated progressive nutritional deprivation through late March. Concurrent increases (P < 0.001) in mean urea nitrogen: creatinine ratios from late February through late March in 3 of 4 areas suggested that increased net catabolism was occurring. Diminished creatinine ratios of sodium and phosphorus reflected low dietary intake of these minerals throughout winter. Mean values and trends of urinary characteristics indicated nutritional deprivation varied among 3 winter ranges in YNP. Continued physiological monitoring of nutritional deprivation, along with detailed examination of other aspects of the bison's ecology, will provide greater insight into the role of ungulate nutrition in the dynamics of such a complex system and improve management.

  8. De Liberto, T.J. & P.J. Urness. 1994. Comparative digestive physiology of American bison and Hereford cattle. In: Proceedings of 1st International Bison Conference, LaCrosse, WI. July 1993.

    ABSTRACT: We reviewed available literature on the nutrition of bison (Bison bison), and provided an overview of our experiments conducted during 1991-92 comparing the digestive physiology of bison and Hereford cattle (Bos taurus). Higher digestion coefficients of dry matter and fiber were found in bison than in cattle, when animals were given free-access to 4,5, and 6% crude protein (CP) rations. However, cattle were apparently capable of compensating for lower digestion coefficients by eating slightly larger quantities of feed. Rumen volatile fatty acids and ammonia nitrogen levels indicated that bison fermented ingesta to a greater extent than cattle, up to 12-hr after feeding. We found no interspecific differences in nitrogen retention on any of the experimental rations. However, serum urea nitrogen and salivary urea nitrogen data suggested more nitrogen was recycled to the rumen in bison than in cattle. We concluded bison digested low-protein, high-fiber feeds more efficiently than cattle, and this was achieved, in part, to a more efficient nitrogen recycling system in bison.

  9. De Liberto, T.J. & P.J. Urness. 1994. Technical Note: A total urine collection apparatus for female bison and cattle. J. Range. Manage. 48: 92-93.

    ABSTRACT: We describe a urinary collection device created specifically for use in metabolism studies on female bison and Hereford cattle. Separating urine from feces, and collecting all urine produced by female animals in metabolism stalls is difficult. Catheters are usually used on animals in confinement, but often with varying degrees of success. Thus, an external device designed to divert urine into collection receptacles was developed. We used the urine collection apparatus successfully in six 8-day metabolism trials conducted during 1991 and 1992.

  10. Dziuk, H.E. 1965. Eructation, regurgitation, and reticuloruminal contraction in the American bison. Amer. J. Physiol. 208: 343-346.

    ABSTRACT: Simultaneous pressure changes in four compartments of the reticulorumen of two young, female bison prepared with rumen fistulas were recorded during eating, ruminating, rest- ing, and insufflation with nitrogen gas. Frequency, magnitude, and duration of contractions were measured in a series of 26 experiments during which the bison were tied in a stanchion. From these measurements it was concluded that reticulorumi- nal motility of American bison is similar to that of domestic cattle. Eructation occurred almost always during contraction of the posterior dorsal blind and dorsal sacs of the rumen. The frequency of eructation was similar to that which was reported previously in cattle and white-tailed deer. During rumination there was an extra reticular contraction during which regurgi- tation occurred.

  11. Evans, L. 1964. Comparison of fatty acids from lipid classes of serum lipoproteins and other lipids in the bison. Journal of Dairy Science. 47: 46-53.

    ABSTRACT: High- (D>1.063) and low-density (D<1.063) lipoproteins, comprised 64 and 36%, respectively, of bison serum total lipids. Protein-bound non-esterified fatty acids accounted for less than 1%. High-density lipoproteins (HDL) contained comparatively greater concentrations of sterol esters, non-esterified fatty acids, and phospholipids. Liver lipids showed 53% triglycerides and 37% phospholipids. Rumen content lipids contained 4, 16, 17, 22, and 33%, respectively, of monoglycerides, triglycerides, sterols, phospholipids, and nonesterified fatty acids. Lipids in abomasal fluid showed 2% monoglycerides, 50% phospholipids, and 12% nonesterified fatty acids. HDL lipid classes resembled those of low-density lipoproteins (LDL) in fatty acid composition, but triglycerides were more saturated and sterol esters more unsaturated in the latter. Oleate was the predominant unsaturated fatty acid in the most of the lipid classes. Glycerides of whole serum and HDL: non-esterified fatty acids of whole serum, HDL, and LDL; and diglycerides of liver tissue were similar in fatty acid composition to the long-chain fatty acids of bison milk fat. Similarity to other ruminant species was noted in the fatty acid composition of rumen content total lipids, liver tissue lipid classes, and milk fat. However, fatty acid patterning of HDL and LDL lipid classes was species-specific.

  12. Hanley, T.A. 1982. The nutritional basis for food selection by ungulates. J. Range Manage. 35: 146-151.

    ABSTRACT: A conceptual framework is outlined for understanding the reasons why ungulates select the kinds of foods that they do. It consists of four morphological parameters: (1) body size and (2) type of digestive system (cecal or ruminant) determine the overall time energy constraints within which the ungulate may forage selectively; (3) rumino-reticular volume to body weight ratio determines the type of food the ruminant is most efficient in processing; and (4) mouth size determines the ability of the ungulate to harvest selectively plant parts of individuals. Principal premises are the following: (1) large ungulates and cecal digestors are more limited by time than are small ungulates and ruminant digestors; (2) high rumino-reticular volume to body weight ratio is an adaptation to exploiting thick cell-walled, high cellulose diets (i.e., graminoids); and (3) low rumino-reticular volume to body weight ratio is an adaptation to exploiting thin but lignified cell-walled diets (i.e., browse).

  13. Hawley, A.W.L. 1981. Effect of bag location along a suspension line on nylon bag digestibiltiy estimates in bison and cattle. J. Range Manage. 34: 265-266.

    ABSTRACT: Erwin and Elliston (1959), Van Dyne (1962), and Quinton (1972) reported that the relative positions of nylon bags suspended within the remen did not significantly affect the digestibilities of forages within the bags. However, digestive capacity varies spatially within the rumen (Balch and Johnson 1950; Miles 1951) and the location of samples within the rumen sometimes affects digestibility estimates (Tomlin et al. 1967). If the nylon bag technique is used in animals fitted with small-diameter cannulae, insertion and removal of the bags is facilitated by arranging the bags in a line (e.g. Van Dyne 1962). The mixing of individual bags with digesta, and hence digestibility estimates, may vary along the line. This experiment was conducted in conjunction with other nylon bag experiments (Hawley et al. 1980) to determine the effect of the location of nylon bags along the suspension line on nylon bag digestibility estimates in bison and cattle.

  14. Hawley, A.W.L. 1987. Bison and cattle use of forages. In: Bison ecology in relation to agricultural development in Slave River lowlands, NWT. Reynolds, H.W. & A.W.L. Hawley, (eds.) Can. Wildl. Serv. pp. 49-52.

    ABSTRACT: North American bison (Bison bison) digested forages native to the Slave River lowlands more efficiently than did Hereford cattle (Bos taurus). Average daily weight gain and feed conversion rates were greater for bison steers than for cattle steers when slough sedge (Carex atherodes) hay was fed in summer. In winter, bison decreased intake of sedge to a maintenance level, and average daily gain and feed conver- sion were greater for Hereford steers. Hereford steer calves also exceeded bison steer calves in gain and feed conversion when a ration exceeding the maintenance requirements of cattle was fed to both species. Physiological differences be- tween bison and cattle in their extraction and use of nutrients were reflected in differences in blood composition.

  15. Hawley, A.W. 1987. Identifying bison ration groups by multivariate analysis of blood composition. J. Wildl. Manage. 51: 893-900.

    ABSTRACT: Discriminant analysis was used to classify animals into ration groups based on blood composition. Blood samples were drawn from groups of 3 bison (Bison bison) steers and 4 Hereford cattle steers receiving 4 rations each in summer and winter (N=56). Four discriminant analyses, 1 for each combination of species and season, were used to classify blood samples into ration groups. Rates of correct classification, evaluated using jackknife procedure, ranged from eleven of 12 winter bison samples to six of 16 summer cattle samples using blood urea nitrogen (BUN), alkaline phosphatase (ALP), and cholesterol (CHOL) as discriminating variables. Classification of summer cattle samples was improved to eleven of 16 by using BUN, total serum protein (TSP), B-globulin (B-GL), and hemoglobin (HGB) as variables. The overall correct classification rate was 79% (44of 56 samples).

  16. Hawley, A.W.L., D.G. Peden, H.W. Reynolds & E. Keith. 1977. Nylon bag digestibilities of five native plants in bison and cattle. Can. J. Anim. Sci. 57: 825.

    ABSTRACT: Dry matter disappearance (DMD) of five native plant species harvested in summer and winter were compared in bison and cattle. Two trials were conducted with two bison and Hereford receiving each of a hay ration and a hay plus grain ration in trial 1, and one bison and one Hereford receiving each ration in trial 2. DMD in this 5 x 2 x 2 x 2 x 2 factorial experiment was measured using the nylon bag technique. Although a statistically significant difference between trials occurred, the magnitude was small and did not alter the interpretation of the other main effects. DMD of plant samples was consistently greater in bison than in cattle, with overall means of 52 and 39%, respectively. DMD of samples tested in bison was not significantly affected by ration, while DMD was decreased by 30% in cattle receiving the grain supplement. This observed difference between bison and cattle was concluded to be in accord with the theory that bison are more efficient in recycling nitrogen. Carex atherodes (DMD=51%) and Salix spp. (DMD=55%) had significantly greater overall DMD values than did Juncus balticus (44%), Geum spp. (40%) and Calamagrostis spp. (40%). DMD values of winter samples were less than those of summer samples, and the magnitude of seasonal change varied among plants.

  17. Hawley, A.W.L., D.G. Peden, H.W. Reynolds & W.R. Stricklin. 1981. Bison and cattle digestion of forages from the Slave River Lowlands, Northwest Territories, Canada. J. Range. Manage. 34: 126-130.

    ABSTRACT: Dry matter disappearance (DMD) of native forages collected from the Slave River Lowlands (SRL), Northwest Territories, was consistently greater in bison (Bison bison) than in Hereford cattle (Bos taurus) when measured with a nylon bag technique. Overall average DMD values were 52% and 39% for bison and cattle, respectively. Mean percent DMD values for each plant species were: willow (Salix spp.), 56; slough hedge (Carex atherodes), 50; baltic rush (Juncus balticus), 47; aleppo avens (Geum aleppicum), 44; and northern reedgrass (Calamagrostis inexpansa), 39. Dry matter disappearance was inversely correlated (P<0.05) with crude fiber content of the sample. Dependence of DMD on crude fiber content was less (P<0.001) in cattle than in bison. Based on relative digestibilities and data on forage intake, we concluded that slough sedge was the most important bison forage in the study area. Average DMD was 44% greater (P<0.01) in a Hereford fed hay than in a Hereford fed hay plus a concentrate supplement. There was no difference (P>0.05) in DMD between two bison fed the hay ration and two fed hay plus the supplement.

  18. Hawley, A.W.L., D.G. Peden, & W.R. Stricklin. 1981. Bison and hereford steer digestion of sedge hay. Can. J. Anim. Sci. 61: 165-174.

    ABSTRACT: The digestibility of sedge hay was measured in six bison (Bison bison) steers and six Hereford (Bos taurus) steers in two total fecal collection trials. The digestion coefficients of all nutrients, except lignin, were significantly greater (P<0.05) in bison than in cattle. For bison and cattle, respectively, overall mean apparent digestibility coefficients, expressed as a percent, were: dry matter, 51.3 and 46.0; crude protein, 38.3 and 27.6; crude fat, 64.2 and 54.4; neutral detergent fiber, 54.7 and 50.0; acid detergent fiber, 47.0 AND 42.4; hemicellulose, 67.1 and 61.7; lignin, 25.2 and 18.7; and gross energy, 50.6 and 45.3. Acid-insoluble ash and lignin were not suitable internal indicators for making species comparisons of digestibilities because of the greater apparent digestion of the indicators by bison. During the summer fecal collection trial, mean daily dry matter intakes of bison and cattle were 1.6 % and 1.4% of body weight, respectively. During the winter trial, the mean daily dry matter intake of cattle (2.0% of body weight) was greater (P>0.05) between bison and cattle in particle size of feed consumed. Greater forage digestibility resulted in greater (P<0.05) average daily gain in bison only in the summer trial, when nutrient consumption by cattle was below the published maintenance requirement of the cattle.

  19. Hawley, A.W.L. & D.G. Peden. 1982. Effects of ration, season and animal handling on composition of bison and cattle blood. Journal of Wildlife Diseases. 18: 321-338.

    ABSTRACT: Composition of ration and season of sampling markedly affected the composition of blood in six tamed bison (Bison bison) steers and eight Hereford cattle (Bos taurus) steers. Observed values extended reported ranges for albumin, phosphorus and blood urea nitrogen (BUN) in bison serum. There were several differences between species in blood composition. In particular, erythrocvtic and BUN values were higher in bison than in cattle. Overall mean values for bison and cattle receiving experimental rations were, respectively BUN, 17.1 mg/dl and 14.1 mg/dl; hemoglobin, 17.8 g/dl and 13.3 g/dl; packed cell volume (PCV), 47.6% and 35.6%; red blood cells, 9.3 X 106/mm3 and 8.2 X 106/mm3; mean corpuscular volume (MCV), 51.3 m3 and 43.5 m3; mean corpuscular hemoglobin, 18.9 pg and 16.1 pg. The significant changes in blood composition associated with changes in ration composition support the use of blood composition as an index of nutritional status. There were no sex-specific differences in blood of 20 bison from Elk Island National Park and 34 bison from Wood Buffalo National Park, Alberta. Alkaline phosphatase (ALP) level was higher in juvenile than in adult bison. Impoundment of wild bison for 24 hr was accompanied by a decrease in BUN and an increase in PCV. Wild bison that were killed during handling had significantly higher blood levels of ALP, glutamate oxaloacetate transaminase, MCV and phosphorus.

  20. Keith, E.O., J.E. Ellis, R.W. Phillips & M.M. Benjamin. 1978. Serologic and values of bison in Colorado. J. Wildl. Dis. 14: 493-500.

    ABSTRACT: Recent economic and aesthetic interest in North American bison (Bison bison) has lead to increased interstate transport of these animals. Serologic and hematologic standards for bison are needed to detect disease in transported animals as well as within herds. This paper describes variation in blood physiological parameters in bison caused by variations in diet and season. Blood was taken from six bison and analyzed for serologic and hematologic parameters. Significant variation was found in blood urea nitrogen, chloride, cholesterol, creatinine, esoinophil, glucose, hemoglobin, lactic dehydrogenase, leukocyte, packed cell volume, potassium, serum globulin, serum glutamic oxalacetic transaminase, SGPT, and sodium levels between animals receiving a high energy-high nitrogen diet and animals receiving a low energy-low nitrogen diet.

  21. Keith, E.O., J.E. Ellis, R.W. Phillips, M.I. Dyer & G.M. Ward. 1981. Some aspects of urea metabolism in North American bison. Acta Theriologica. 26: 257-268.

    ABSTRACT: Previous studies comparing the digestive capacity of bison (Bison bison) with that of cattle (Bos taurus) indicated that bison may digest low-quality forage to a greater extent than cattle. In an attempt to determine the relationship between digestive ability and whole animal nitrogen budget, we measured urea concentrations in the blood , in the saliva, in the urine, and in the rumen of two groups of bison; one fed a high-protein diet, the other fed a low-protein diet. We found differences between groups in urea levels in some body pools but not in others. Results suggest that urea metabolism in bison responds to dietary N-levels, but further research is needed to clarify this response.

  22. Knox, K.L., D. Wesley, J.C. Crownover & J. Nagy. 1974. Comparative energy metabolism of American ungulates. Publ. Eur. Assoc. Anim. Prod. 14: 229-232.

    ABSTRACT: The data reported in this paper suggests that fasting heat production of North American wild ruminants is lower than reported values for wild ruminants in other parts of the world. This difference may merely reflect the differences in training of animals to the conditions of metabolic chambers. Secondly, the data suggests that antelope efficiently utilized dietary energy at the level equal to or greater than domestic ruminants. Fasting heat production values for all animals studied except sheep were found to be higher than the inter-species value reported by Kleiber (1961). Considering the variation in experimental conditions and animal variability this difference is not surprising.

  23. Marler, R.J. 1975. Some hematologic and blood chemistry values in two herds of American bison in Kansas. Journal of Wildlife Diseases. 11: 97-100.

    ABSTRACT: The data presented are compiled from two herds of American bison (Bison bison) in Kansas. In this study there were differences in the mean values of white blood cell count, neutrophil percentage, lymphocyte percentage and cholestrol, alka- line phosphatase, specific glutamic-oxalacetic transaminase concentrations between the age groups of animals under 2 years of age and bison over 2 years old. Dif- ferences in the two age groups paralleled those found in Jersey and Hereford cattle. Packed cell volume and hemoglobin concentration was considerably higher than found in domestic Bovidae. More data is needed from other bison herds in this country to better describe the range of normal variation in individuals, population and age groups of B. bison.

  24. Mehrer, C.F. 1976. Some hematologic values of bison from five areas of the United States. Journal of Wildlife Diseases. 12: 7-13.

    ABSTRACT: Seventeen hematologic values of the American bison (Bison bison) from five areas of the United States were determined using standard techniques. The means of the principal blood measurements for all bison were 10.08 +/- 1.43 million ery- throcytes/mm3, 8.03 +/ - 1.41 thousand leukocytes/mm3, 16.92 +/- 1.43 gm % hemo- globin and 47.11 +/- 4.06% hematocrit. There was a significant variation (P < 0.05) among age groups of males for erythrocytes, neutrophils, lymphocytes and mono- cytes. However, no significant variation between female age groups or sexes was found for any of the blood cell values determined.

  25. Pearson, H.A. 1967. Rumen microorganisms in buffalo from Southern Utah. Applied Microbiology. 15: 1450-1451.

    ABSTRACT: Rumen microbial populations from buffalo (Bison bison Linn.) in southern Utah were identified on the basis of their morphology and staining characteristics. The rumen bacteria and ciliate protazoa were similar in number and kind to those found in domestic livestock.

  26. Peden, D.G. 1971. Preliminary activities and results in bison research on the Pawnee site. Technical Report No. 121. Natural Resource Ecology Laboratory, Colorado State University, Fort Collins, Colorado. pp. 1-8.

    ABSTRACT: This report covers activities and preliminary results of the bison project during the period between September 1969 and early 1971. Data given herein pertain to that collected at the U.S. IBP Grassland Biome Site, Pawnee. A general outline for 1971 collections is given.

  27. Peden, D.G., G.M. Van Dyne, R.W. Rice & R.M. Hansen. 1974. The trophic ecology of Bison bison L. on the shortgrass plains. J. Appl. Ecology. 489-497.

    ABSTRACT: (1) Seasonal information on dietary composition, forage digestibility and selectivity was collected for bison, cattle and sheep from two treatments representing lightly grazed and heavily grazed pasture. (2) Bison have a greater preference for warm-season grasses and appear to feed less selectively than cattle and in different areas within shortgrass vegetation. (3) Sheep consume fewer grasses than either species. (4) Bison appear to have a greater digestive power than cattle when consuming low protein, poor quality forage, and may also consume greater quantities of forage as compared to cattle. (5) These two mechanisms of feeding strategies may permit bison to exploit more fully than cattle the herbage resources on shortgrass plains.

  28. Peters, H.F. 1958. A feedlot study of bison and cattle and Hereford calves. Can. J. Anim. Sci. 38: 87-90.

    ABSTRACT: Time-constant feedlot experiments were conducted in 1952-53 and 1956-57 with bison, cattalo and Hereford bulls and heifer calves at the Canada Range Experimental Farm, Manyberries, Alberta. The Cattalo made significantly greater feedlot gains than bison and lower gains than Herefords in both experiments. There was a significant reduction in carcass grade, a reduction in proportion of carcass weight in the hind quarters, and an increase in dressing percentage as the proportion of bison breeding increased.

  29. Reynolds, H.W., R.M. Hansen & D.G. Peden. 1978. Diets of the Slave River Lowland bison herd, Northwest Territories, Canada. J. Wildl. Management. 42: 581-590.

    ABSTRACT: Microhistological examination of fecal samples was used to determine diets of free-ranging bison (Bison bison) from the Slave River lowlands in the Boreal Forest Region of northern Canada. Slough sedge (Carex atherodes) and reedgrasses (Calamagrostis spp.) were the most common range plants, comprising, respectively, 49 and 18 percent composition of wet meadows and 1 and 64 percent of dry meadows. Net annual yield of above-ground plant biomass for wet meadows (4,400 kg/ha) significantlv exceeded that for dry meadows (2,280 kg/ha). Seasonal bison diets contained 29 different plant categories of which 12 contributed over 1 percent in at least 1 season. Slough sedge and reedgrass were the most common foods for bison at all seasons, ranging, respectively, from 42 and 35 percent composition in winter to 77 and 15 percent in spring. Bison selected major food items in a similar rank order throughout the year regardless of changes in relative proportions and number of plant species ingested. Feeding preference for wet habitat was shown. Annual herbage production did not appear to be a population-limiting factor.

  30. Rice, R.W., J.G. Nagy & D.G. Peden. 1971. Functional interaction of large herbivores on grasslands. In: Preliminary analysis of structure and functions in grasslands. N.R. French, (ed.), Range Science Department. Series No. 10, pp. 241-265.

    ABSTRACT: The herbivore forms a link in the food chain of man by degrading plant structural carbohydrates which are not utilized directly by improvement of nutritive value of primary plant production, by the use of poor quality protein and nonprotein nitrogen for synthesis of high quality protein, and by the synthesis of the B vitamins and vitamin E. The herbivore also harvests primary production where topography or productivity precludes other harvesting methods. The herbivore also accelerates the decomposition of plant biomass. The U.S. IBP Grassland Biome large herbivore group is studying the impact and interrelation of the pronghorn antelope, American bison, domestic cow, and sheep on grasslands. Studies to date indicate that there is a similar basal metabolic relationship among these herbivores. Their functional interaction should be described in terms other than metabolic efficiency. The American bison was shown to have a higher digestive power than domestic cattle on grassland forages; the difference was greater when mature forages were consumed. The utilization of diets by cattle was not greatly different according to grazing intensity. Summer diets had a higher nutritive value than spring or winter diets. Cattle on the heavily grazed pasture ate a larger proportion of grass, forbs, and shrubs than those on the light use pastures. Cattle gained more per head on the light use pasture whereas a total gain per hectare was greater on the heavy use pasture. Differences in cattle productivity were largely due to differences in the total intake of forage per individual animal or per pasture and on diet utilization. Antelope consumed a higher quality diet than cattle regardless of the season; cattle ate a higher proportion of grasses than antelope while antelope ate more forbs and the half-shrub fringed sagewort. The similarity of cattle and antelope diets was affected by seasons; the diets were least similar during the growing season when selection opportunity was greatest and most similar during the winter, with fewer varieties of plants available and with all plants more mature. Dietary comparisons among summer diets of antelope, bison, cattle, and sheep were made; cattle and bison ate the most similar diets, while antelope ate diets least similar to other herbivores; sheep were intermediate between cattle, bison, and antelope in dietary habits. Preliminary observations on grazing behavior indicate that location of grazing and season are important factors influencing herbivore interaction. Preliminary optimization of primary production used by herbivores indicates that mixtures of herbivores should be more efficient secondary producers from grasslands than single species.

  31. Rice, R.W., R.E. Dean & J.E. Ellis. 1973. Bison, cattle and sheep dietary quality and food intake. J. Anim. Sci. 38: 1332.

    ABSTRACT: Esophageal samples of diet were collected with fistulated bison, cattle and sheep. The animals were grazing on the IBP Intensive Study Site of the Grasslands BIOME which consisted of shortgrass native rangeland, dominated by blue grama (Bouteloua gracilis). Diet samples were analyzed for cell wall constituents, acid detergent fiber and acid detergent lignin. In vitro dry matter digestion was determined. Fecal excretion was estimated with chromic oxide as an external indicator. Cell wall constituents averaged 62, 60 and 95%, acid detergent fiber was 53,49 and 44% while acid detergent lignin was 9, 10 and 12% for bison, cattle and sheep, respectively. The analyses indicated that dietary quality was lowest for bison followed by cattle and sheep. In vitro dry matter digestibility of diet samples ranked bison < cattle < sheep. Relative intake estimates (g/kg w3/4) determined from fecal excretion and in vitro digestion were greatest for bison followed by cattle then sheep. Sheep were more selective grazers than cattle with bison being the least selective. It appears that non-selective grazers compensate for overall poorer dietary quality by consuming larger quantities of food while grazing. This study was supported in part by NSF Grants GB-31862X and GB-31862X2 to the IBP, Grassland BIOME for Analysis of Structure, Function and Utilization of Grassland Ecosystems.

  32. Richmond, R.J., R.J. Hudson & R.J. Christopherson. 1977. Comparison of forage intake and digestibility by bison, yak and cattle. Acta Theriologica. 22: 225-230.

    ABSTRACT: Feed intake, selectivity and apparent digestibility coefficients of dry matter, protein and detergent fiber fractions were determined in groups of four yearling bison, yak and cattle. Diets of contrasting quality for these comparisons were provided by native sedge meadow hay, bromefescue grass hay and alfalfa hay. Feed intakes for bison and cattle were similar but considerably higher on a per unit body weight basis than for yak. Apparent digestibility coefficients for dry matter and detergent fiber fractions tended to be highest in bison followed by yak then cattle, a digestive superiority which was most marked on the grass hay diet. However, off-setting the digestive advantage of bison in relation to the other species was an apparent higher digestible dry matter requirement for maintenance. Gains and feed conversion for cattle exceeded those of yak and bison on sedge and grass hays but not on alfalfa.

  33. Schaefer, A.L., B.A. Young & A.M. Chimwano. 1978. Ration digestion and retention times of digesta in domestic cattle (Bos taurus), American bison (Bison bison), and Tibetian yak (Bos grunniens). Can. J. Zool. 56: 2355-2358.

    ABSTRACT: Digestive functions, digesta retention times, and plasma thyroid hormone concentrations were measured in three species of Bovidae: domestic cattle (Bos taurus; three breeds), American bison (Bison bison), and Tibetan yak (Bos grunniens), fed a pelleted ration (nitrogen, 2.62%) at a near maintenance level. Apparent digestibilities of dry matter, enery, and nitrogen components of the ration were not significantly different among animal groups except for one breed of cattle (Holstein-Friesian) which had higher dry matter and energy digestibilities than all the other animal groups and a higher nitrogen digestibility than the other breeds of cattle. Nitrogen disappearance from the gastrointestinal tract (apparent absorption) per 100g of dry matter digested was greater in the bison and yak than in the cattle, and mean retention time of digesta in the gastrointestinal tract was 65-69h in the cattle, compared with 79 and 78h in the bison and yak, respectively. The longer total retention time of digesta in the bison and yak may account in part for their apparent improved nitrogen economy and greater ability to digest fibrous feed material.

  34. Short, R.E., L.F. James, K.E. Panter, R.B. Staigmiller, R.A. Bellows, J. Malcolm & S.P. Ford. 1992. Effects of feeding Ponderosa pine needles during pregnancy: comparative studies with bison, cattle, goats, and sheep. J. Anim. Sci. 70: 3498-3504.

    ABSTRACT: : Four experiments were conducted to determine the effect of feeding dried pine needles (Pinus ponderosa; PN) on the abortion rate of ruminants. In Exp. 1, cattle were fed 5.4 kg of PN daily for 21 d starting at 116, 167, 215, or 254 d of pregnancy. The PN did not cause abortions when started at 116 d; thereafter, the percentage of cows that aborted increased linearly, and the interval to abortion decreased linearly (both P < .01); all cows fed PN beginning at 254 d aborted. In Exp. 2, cattle were fed .7, 1.4, or 2.7 kg of PN for 21 d or 2.7 kg for I or 3 d. Sheep and goats were fed .8 and .5 kg of PN, respectively, starting at 121 d of pregnancy. The PN induced some abortions in cattle when fed for 1 (11%) or 3 (30%) d, but the abortion rate was greater (P < .01) when the PN were fed for longer periods of time (80, 90, and 100% aborted in 19, 17, and 10 d for .7-, 1.4-, and 2.7-kg doses, respectively.). No goats or sheep aborted in response to PN feeding. Pregnancy rates during the next breeding season for cows that aborted in response to the PN were slightly higher than rates for control cows (94 vs 87%). In Exp. 3, buffalo (Bison bison) and cattle were fed 2.25 kg of PN from the same collection.
    Abortions were induced in all buffalo and cattle that were fed PN. In Exp. 4, low amounts (. 11 and .34 kg) of PN were fed to cattle for 40 d before the start of feeding of 1.35 kg of PN at 255 d of pregnancy. Low amounts of PN did not induce abortions, but .34 kg delayed abortions after the 1.35-kg level was fed (P < .01). In all experiments aborted fetuses were alive, all cows (both buffalo and cattle) that aborted had a retained placenta, and calf survival was dependent on maturity at the time of parturition. Our conclusions are as follows: 1) consumption of PN caused abortions in a majority of cows in late pregnancy; 2) the response increased with advancing stage of pregnancy, increased dose of PN, and greater length of exposure, but supplemental vitamin A was not prophylactic; 3) buffalo responded similarly to cattle, but neither goats nor sheep were affected by PN; 4) fertility was not affected by PN; 5) PN were not directly toxic to calves, and survival of calves was dependent on maturity at the time of parturition; and 6) compensatory mechanisms were triggered when subthreshold doses of PN were fed.

  35. Sikarskie, J.G., T. Schillhorn Van Veen, D.E. Ullrey & M.D. Kock. 1989. Comparative serum selenium values for ranched and free-ranging American bison, (Bison bison). J. Zoo Wildl. Med. 20: 34-38.

    ABSTRACT: Serum samples were obtained from 20 randomly selected American bison (Bison bison) at a ranch in Michigan with a herd history of selenium (Se) deficiency, including white muscle disease/capture myopathy in spite of Se supplementation. Samples also were obtained from 20 free- ranging bison in the Badlands National Park, South Dakota, which were age and sex matched with the Michigan bison. Animals from both groups were handled similarly, with capture, physical restraint, and blood collection occurring at the same time of year (early fall) and serum frozen for later Se analysis. Exertion and stress have been implicated in the etiology of capture myopathy so the method of restraint and its impact on serum Se values also was investigated. Samples from 20 unexcited South Dakota bison, chemically restrained with carfentanil citrate and xylazine hydro- chloride administered via tranquilizer dart from ambush, also were analyzed. Mean serum Se was 0.026 mg/ml for Michigan bison, which was lower (P < 0.01) than the 0.099 mg/ml for similarly restrained bison from South Dakota. Mean serum Se of the anesthetized South Dakota bison was 0.101 mg/ml, which was not different (P > 0.05) from the mean for serum collected from physically restrained bison from the same area. Serum Se values from bison in South Dakota compared well with values considered adequate for domestic cattle and other wild species, while the low values from Michigan bison indicated a need for greater supplementation to balance the regional deficiencies of Se in forage plants.

  36. Sikarskie, J.G., T. Schillhorn Van Veen, G. van Selm & M.D. Kock. 1990. Comparative blood characteristics of ranched and free-ranging American bison (Bison bison) Am. J. Vet. Res. 51: 955-957

    ABSTRACT: Blood samples were obtained from 20 bison (Bison bison) from a ranch in northern lower Michigan, as well as from 20 free-ranging bison of the same sex and similar age from the Badlands National Park in South Dakota. Hematologic and serum biochemical values were deter- mined. The values were comparable in both groups, ex- cept for those for BUN, aspartate transaminase, and phosphorus, which were significantly (P < 0.001) higher in the ranched bison than in the free-ranging bison. These differences were attributed to nutritional effects. Impact of age on blood characteristics was assessed in the ranched bison only by comparing values from calves weighing less than 185 kg with those from bison weighing more than 185 kg. Calves had significantly (P < 0.001) higher val- ues for phosphorus and RBC counts and lower total protein values than adults. Adult bison had higher eosinophil and neutrophil counts with lower numbers of lympho- cytes, suggestive of a stress leukogram, whereas calves had the typical bovine neutrophil:lymphocyte ratio.

  37. Stanton,T.L., D. Schutz, W. McFarlane, R. Seedig & D. Stewart. Effects of concentrate level in bison finishing rations on feedyard performance.

    ABSTRACT: One hundred ninety-two dehorned bison bulls were utilized in a completely randomized design with initial weight equalized to evaluate the effect of concentrate levels of 30, 50, and 90% in finishing diets on 266 day feedyard performance. There were 8 head/pen and 6 pens/treatment. On day 170 the 30% concentrate level was increased to 70% and protein was reduced to 10% from 12% CP. Feed intake was not affected by treatment. However, feed intake appeared to be affected seasonally (lower in winter than summer or fall). Feeding bison 70 % or 90 % concentrate through 169 days on test improved (P < .05) gain over bison fed 30 or 50 % concentrate. Feeding 70 % concentrate finishing diets to bison improved (P < .05) feed efficiency compared to the 30 or 50% concentrate diets during days 0-169. Seasonality or short day length appeared to have a large negative impact on feedyard performance of bison bulls.

  38. Towne, G., T.G. Nagaraja, R.C. Cochran, D.L. Harmon, C.E. Owensby & D.W. Kaufman. 1988. Comparisons of ruminal fermentation characteristics and microbial populations in bison and cattle. Appl. Environ. Microbiol. 54: 2510-2514.

    ABSTRACT: Ruminal microbial populations, fermentation characteristics, digestibility, and liquid flow rates in two ruminally cannulated bison and two ruminally cannulated Hereford steers fed a prairie hay diet were compared. No significant differences in anaerobic bacterial counts, volatile fattv acid concentrations, or ruminal pHs were evident between bison and cattle. Also, no significant differences in neutral detergent fiber digestibility, indigestible fiber retention time, or intake were detected between bison and cattle, although cattle had higher levels (P < 0.08) of ruminal dry matter and indigestible fiber than bison. Bison had a smaller (P = 0.02) ruminoreticular volume, faster liquid dilution rates, and faster liquid turnover times than cattle. The average ruminal ammonia nitrogen concentration was higher (P = 0.02) in bison (1.17 mg/dl) than in cattle mg/dl). Total ciliate protozoal counts and cell volume were greater (P = 0.07) in bison (32.8 x 10 4/g and 407.1 X 10 -4ml/g , respectively) than in cattle (15.7 x 10 4 /g and 162.2 x 10-4 ml/g, respectively. Bison harbored higher (P < 0.02) numbers of Dasytricha spp., Eudiplodinium maizgii. Ezidiplodinium bursa, and Epidinium spp. than cattle and possessed a type B protozoan population. The cattle possessed a mixed type A-tvpe B population that was characterized by Ophryoscolex spp. and Polyplastron spp. in association with low concentrations of Epidinium spp. and Eudiplodinium maggii.

  39. Towne, G., T.G. Nagaraja & K.K. Kemp. 1988. Ruminal ciliated protozoa in bison. Appl. Environ. Microbiol. 54: 2733-2736.

    ABSTRACT: Ruminal contents from 79 slaughtered bison and 2 ruminally cannulated bison were collected to obtain information on total numbers and species distribution of ciliated protozoa. The bison originated from numerous herds throughout the Great Plains and were grouped into three dietary categories: (i) only forage; (ii) forage with moderate levels of supplementation; and (iii) feedlot concentrate-silage diet. Total ciliate counts were highest in bison receiving grain supplementation (210.1 x 104/ g) and lowest in bison consuming only forage (27.1 x 104/g) . All protozoan species found in bison have been reported in domestic livestock, although Ophryoscolex sp., a relatively common protozoan in cattle, was detected at low concentrations in only eight bison. The uncommon holotrich Microcetus lappus was present in five bison in concentrations reaching 8.4% of the total ciliate population. Charonina ventriculi, another infrequently observed species, was present in 18 bison, with the highest concentrations in forage-fed animals. Thirty bison possessed a type B protozoan population, characterized by Epidinium sp., Eudiplodinium maggii, and Eudiplodinium bovis. Thirty-eight bison possessed a mixed A-B population, characterized by Polyplastron sp. coexisting with low numbers of Eudiplodinium maggii or Epidinium sp. or both. Thirteen bison possessed populations lacking any remnant type B ciliate species. At least 29 of the bison possessing Polyplastron sp. were known to have been in contact with cattle, whereas all bison isolated from cattle had type B populations. The reduction of type B populations in bison becomes increasingly likely as bison production expands into areas inhabited by domestic livestock.

  40. Towne, G., T.G. Nagaraja & R.C. Cochran. 1989. Ruminal microbial populations and fermentation characteristics in bison and cattle fed high- and low-quality forage. Microb. Ecol. 17: 311-316.

    ABSTRACT: Ruminal microbial populations and fermentation products were compared between two ruminallv cannulated bison (375 kg) and two ru- minally cannulated Hereford steers (567 kg) on alfalfa or prairie hay diets. Differential media were used to enumerate carbohydrate-specific bacterial subgroups. Voluntary dry matter intake was higher (P = 0.006) for cattle than for bison fed alfalfa, but prairie hay intake was not different (P = 0. 16) between the two species. Volatile fatty acid concentrations, pH, and ruminal ammonia were similar between bison and cattle on both diets. Total an- aerobic bacteria and xylanolytic bacterial counts were higher (P < 0.02) in bison than in cattle fed alfalfa. However, with the prairie hay diet, no differences in bacterial counts on any medium were observed between ruminant species. Both bison and cattle possessed a mixed A-B protozoan population with nearly identical protozoan numbers and distribution of genera. The similarities between bison and cattle consuming either high- or low-quality forage suggest that any differences in putative forage di- gestibility between the species are not due to differences in microbial counts.

  41. Towne, G. & T.G. Nagaraja. 1989. Occurrence and diurnal population fluctuations of the ruminal protozoan Microcetus lappus. Appl. Environ. Microbiol. 55: 91-94.

    ABSTRACT: A series of experiments with bison and cattle were conducted to obtain information on the relatively uncommon ruminal protozoan Microcelus lappus. Although M. lappus is a holotrich, diurnal changes in concentrations indicate that it follows a cycle unlike most other holotrichs, decreasing shortly after feed is offered and then gradually increasing over time. Concentrations of M. lappus varied widely among animals, exceeding 50% of the total protozoan population in some cattle. In bison, Microcetus concentrations averaged 2% of the protozoan population. Dietary protein and energy levels apparently did not influence Microcetus numbers. The highest concentrations of M. lappus were found in the reticulum, whereas the lowest numbers occurred in the mid-dorsal sac.

  42. Towne, G. & T.G. Nagaraja. 1990. Omasal ciliated protozoa in cattle, bison, and sheep. Appl. Environ. Microbiol. 56: 409-412.

    ABSTRACT: Omasal contents were collected from slaughtered cattle (n = 54), bison (n = 15), and sheep (n = 40) to determine numbers and generic distribution of ciliated protozoa. Total protozoan numbers were significantly lower in omasal contents than in ruminal contents of all three species, but the percent composition of all protozoan genera was similar between omasal and ruminal populations. The highest numbers of omasal protozoa found were 7.61 x 105/g in cattle, 7.01 x 10'/g in bison, and 1.29 x 106/g in sheep. Omasal dry matter was significantly higher than ruminal dry matter in all species and ranged up to 51.5% in cattle fed high-concentrate diets. The omasal pH was similar to the ruminal pH in all species. The number of omasal laminae averaged 149, 145, and 74 for cattle, bison, and sheep, respectively. Although protozoan concentrations in omasal contents were approximately 80% lower than those in ruminal contents, the omasum harbored relatively high numbers of ciliated protozoa. The resident omasal protozoa are extremely difficult to remove, particularly in cattle, and apparently are responsible for reinoculating transiently defaunated rumens.

  43. Van Vuren, D. & M.P. Bray. 1983. Diets of bison and cattle on a seeded range in Southern Utah. Journal of Range Management. 36: 499-500.

    ABSTRACT: Diets of bison (Bison bison) and cattle (Bos taurus) were evalu- ated on a southern Utah range seeded to crested wheatgrass (Agro- pyron desertorum) and alfalfa (Medicago sativa). Bison feces comprised %% grasses and sedges, 4% forbs, and 1% shrubs. Cattle feces comprised 88% grasses and sedges, 4% forbs, and 8% shrubs. Diets were 91% similar, indicating a high potential for competition between bison and cattle.

  44. Van Vuren, D. 1984. Summer diets of bison and cattle in Southern Utah. Journal of Range Management. 37: 260-261.

    ABSTRACT: Diets of bison (Bison bison) and cattle (Bos taurus) were evaluated in a shrub-steppe plant community in the Henry Mountains, Utah. Bison feces comprised 99% grasses and sedges and 1% forbs. Cattle feces also were primarily grasses and sedges (95%), but in addition included significantly more forbs (5%) than did bison feces.

  45. Varel, V.H. & B.A. Dehority. 1989. Ruminal celluloytic bacteria and protozoa from bison, cattle-bison hybrids, and cattle fed three alfalfa-corn diets. Appl. Environ. Microbiol. 55: 148-153.

    ABSTRACT: Ruminal cellulolytic bacteria and protozoa and in vitro digestibility of alfalfa fiber fractions were compared among bison, bison hvbrids, and crossbed cattle (five each) when they were fed alfalfa and corn in a ratio of 100:0, 75:25, and 50:@-0, respectively. The total number of viable bacteria (2.16 x 109 to 5.44 x 109/mi of ruminal fluid) and the number of cellulolytic bacteria (3.74 x 107 to 10.9 X 107/Mi) were not different among groups of animals fed each diet. The genera of protozoa in all of the animal groups were similar; however, when either the 100:0 or 50:50 diet was used the percentage of Entodinium sp. was lower and the percentage of Diplodiniinae was higher (P < 0.05) in bison than in bison hybrids or cattle. Bacteroides succi .nogenes made up the largest number of cellulolytic isolates from bison (58 and 36%, respectively, on the 100:0 and 75:25 diets), which were more numerous (P < 0.05) than those from bison hybrids (36 and 12%) and cattle (33 and 18%). This was offset by a lower number of cellulolytic Butyrivibrio isolates. The numbers of Ruminococcus albus and R. flavefaciens isolates, in general, were similar among the bovid species, although R. flavefaciens generally made up less than 10% of the cellulolytic isolates. In vitro digestibility coefficients were greater (P < 0.05) for the bison when the 75:25 diet was used and similar for the other two diets. The concentration of ruminal volatile fatty acids was larger (P < 0.05) in bison than in bison hybrids and cattle when the 50:50 diet was used. Results from this study indicate that the percentages of protozoan genera and cellulolytic bacterial species in bison are different from those of bison hybrids and cattle, suggesting that metabolic differences exist among these animal groups.

  46. Vestweber, J.G., D.E. Johnson, G.L. Merrill & J.J. Staats. 1991. Hematological and blood chemistry profiles of American bison grazing on Konza prairie of Kansas. Journal of Wildlife Diseases. 27: 417-420.

    ABSTRACT: Normal hematological and blood chemistry parameters were measured in 45 Amer- ican bison (Bison bison) that were divided into three age groups for comparison. There was a statistically significant (P < 0.05) increase with advancing age in mean corpuscular volume, mean corpuscular hemoglobin, absolute neutrophil and eosinophil counts, total protein, globulin, cre- atinine, and blood urea nitrogen. There was a statistically significant (P < 0.05) decrease with advancing age in levels of sorbital dehydrogenase, alkaline phosphatase, glucose, sodium, calcium and phosphorus.

  47. Wilber, C.G. & T.W. Gorski. 1955. The lipids in Bison bison. J. Mammal. 36: 305-308.

  48. Young, B.A., A. Schaefer & A. Chimwano. 1976. Digestive capacities of cattle, bison, and yak. Annual Feeder's Day Report. 56: 31-34.

    ABSTRACT: Holstein, Hereford, and Scottish Highland cattle and bison and yak were compared in respect to their capacity to digest dietary components in an attempt to identify the cause of apparent differences in digestive efficiencies. The Holstein cattle were more capable than the other animals in digesting dry matter and energy. The reason for the high efficiency of the Holstein cattle was not identified. The apparent digestibilities of protein were above average in the Holsteins, bison and yak and the protein absorbed per 100, grams of dry matter digested tended to be higher in the bison and yak than in the cattle. The high absorption of protein relative to dry matter in the bison and yak may have been associated with the longer time for passage of ingesta through their digestive tract. In addition to their slow passage of ingesta, the bison and yak also had low plasma concentrations of thyroxine.

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