Growth Promoting Implants and Nutrient Restriction Prior to Feeding: Effect on Carcass Composition, Carcass Quality, and Consumer Acceptability of Beef

Implant strategy and nutrient restriction prior to finishing may alter feedlot performance, as well as carcass characteristics and consumer acceptability of beef. The objectives of these studies were to determine the effect of prefinishing implant strategy and plane of nutrition on prefinishing and feedlot performance, carcass characteristics and quality, and consumer acceptability of beef. In 2 experiments, spring-born calves were weaned in the fall (Exp. 1, n =120; and Exp. 2, n = 96) and were either finished as calves (CALF-FED) or placed on a growing program with a target ADG of 0.45 kg/d (RSTR) or 0.91 kg/d (UNRSTR) before finishing. Half of each backgrounding group received moderate potency combination hormonal implants (Synovex-S/H; Pfizer Animal Health, Madison, NJ) before finishing (IMPL). At arrival to the feedyard all cattle were implanted with a moderate potency implant and were reimplanted following 100-d (CALF-FED) or 81-d on feed (UNRSTR and RSTR). Animal performance and carcass characteristics data were analyzed as a split plot design using the Mixed procedure of SAS. Treatment least-squares means were separated using predicted differences. Implantation prefinishing positively affected (P \u3c 0.01) ADG in UNRSTR cattle in the feedlot in Exp. 1, and in all growth treatment groups (P \u3c 0.01) in Exp. 2. Cattle in the UNRSTR treatment had greater (P \u3c 0.01) HCW than CALF-FED or RSTR in both experiments, but there was no effect (P = 0.38) of implant on HCW. Cattle fed as calves had a greater (P = 0.02) marbling score than yearlings in Exp. 1, but there were no differences (P = 0.32) in marbling scores across treatments in Exp. 2. In Exp 1, IMPL cattle tended (P = 0.06) to have a lower marbling score and had reduced (P = 0.03) percentage of cattle grading Choice; however, there was no effect (P ≥ 0.32) of implant strategy on the percentage of cattle grading Choice or on marbling score. Cattle receiving an implant prefinishing had less (P ≤ 0.03) initial and sustained tenderness than cattle that received a delayed implant in Exp 1 and 2