Influence of Finishing Systems on Carcass Characteristics, Composition, and Fatty Acid Profile of Bison Bulls

Abstract

The objective of this study was to determine the influence of grain- and grass-finishing systems on carcass characteristics of bison bulls and proximate and fatty acid compositions of bison steaks. Bison bulls grazed native pasture until approximately 25 mo of age, then were randomly assigned to grain-finishing (n=98) or grass-finishing (n=98) treatments. Bulls were slaughtered at approximately 30 mo of age. Hot carcass weight (HCW), ribeye area, backfat thickness, kidney fat percentage, marbling score, and instrumental color (L*,a*, and b*) of the ribeye and subcutaneous fat were recorded. Skeletal maturity, lean maturity, and fat color were subjectively scored. Strip loins were collected from a sub-sample of carcasses, fabricated into 2.5-cm steaks, and designated for proximate, cholesterol, or fatty acid analyses. Grain-finished bulls had greater (P<0.0001) HCW, dressing percentage, ribeye area, backfat thickness, kidney fat percentage,and marbling score. The a* and b* values of the ribeye and a* value of subcutaneous fat were greater (P<0.0001), but the L* and b* values of subcutaneous fat were less (P<0.0001) for grain-finished bulls. A greater proportion (P<0.001) of grain-finished carcasses had moderately bright red lean color, whereas a greater proportion (P<0.0001) of grass-finished carcasses had moderately yellow fat color. Steaks from grain-finished bulls had an increased percentage of crude protein (P<0.0001), fat (P<0.0001), and ash (P=0.0006) content but less moisture (P<0.0001). Steaks from grain-finished bulls had more (P<0.001) cholesterol and palmitic, stearic, oleic, linoleic, and arachidonic acids in addition to more total fatty acids (mg/g of wet tissue). However, for total fatty acids, grass-finished steaks had a greater (P<0.0001) percentage of polyunsaturated fatty acids. These data indicate that the finishing system influences the composition of bison bull carcasses as well as the nutrient profile of bison meat.