Chairperson, Graduate Committee: Jane A. Boles.Perz, Katharine Anna2013-06-252013-06-252013https://scholarworks.montana.edu/handle/1/2044Reducing variation in tenderness is a goal for the meat industry. The objective of this study was to determine if different growth patterns, not caused by nutrient restriction, impacted carcass characteristics and tenderness. Simmental x Angus steers (n = 18) reared under similar conditions, fed in the same pen at the feedlot, were allocated into fast (n = 9) and slow (n = 9) growing groups based upon four sets of weight data. After slaughter, carcass data were obtained. The striploin was removed, cut into steaks, and aged for 1, 3, 7, 14, and 21 days. For each aging period, one steak per steer underwent evaluation of shear force and MFI. Myofibrils were isolated from aged muscle samples and protein degradation was visualized with the use of SDS-PAGE. Carcass weight (P< 0.0001) and LD area (P = 0.0093) were significantly affected by growth rate. Shear force (P = 0.0003) and MFI (P< 0.0001) were significantly affected by length of aging, but not by growth rate (P> or = 0.3184); nor was there a significant interaction between growth rate and length of aging (P> or = 0.6555). Even though the shear force x growth rate finding was not statistically significant, shear force of steaks from fast-growing animals had a greater reduction in shear force values indicating a difference in early tenderization. A currently unidentified protein with a molecular weight between 130 and 100kDa was seen earlier postmortem in more tender muscle. This degradation was more apparent in muscle from fast growing steers. A 30kDa component also appeared earlier, and at a greater band intensity, in more tender muscle. Degradation of the 30kDa component was also more evident in fast growing steers. These results suggest that there is a difference in protein degradation in muscle from animals with differing growth paths. The results of this study suggest that more research is warranted to identify differences in protein degradation due to growth rate and to elucidate the effect of growth rate on variation in tenderness.enCattleGrowthBeefFood--QualityThesisCopyright 2013 by Katharine Anna Perz