Mississippi Farm to Feedlot Program 13-year summary: Effects of steer age and morbidity on feedlot performance and carcass traits1

Records of steers (n = 6,392) consigned to the Mississippi Farm to Feedlot Program from 1993 to 2006 were used to assess effects of steer age and morbidity on feedlot performance and carcass traits and to describe characteristics of steers fitting certain carcass specifications by finishing net return quartile ranking. Morbidity rate, days treated, treatment cost, and mortality rate were dramatically greater (P < 0.05) for steers ≤ 180 d of age at feedlot entry than for older steers. These health-related variables were all least (P < 0.05) for cattle at least 361 d of age at feedlot entry. The percentage of steer carcasses grading Choice or better increased (P < 0.05) with advancing calf age. Healthy steers were older at feedlot entry (P < 0.01) and had greater (P < 0.0001) initial BW than did treated steers. Marbling score, USDA QG, calculated YG, dressing percentage, and backfat thickness were greater (P < 0.01) for carcasses from healthy versus treated steers. Steers producing greater finishing net return had lesser (P < 0.0001) morbidity rate, days treated, and treatment cost and greater (P < 0.0001) initial BW, feedlot ADG, final BW, HCW, marbling score, USDA QG, backfat thickness, LM area, LM area per unit HCW, and calculated YG. Steer age at feedlot entry and morbidity affect finishing performance and carcass characteristics. Characteristics of the most profitable steers for finishing and slaughter include faster-growing, less morbid calves with heavier carcasses.