Effect of Weight at Castration on Steer Performance in the Feedlot

One hundred eighty-eight male calves were randomly assigned to one of five treatments at about 6 wk of age t o determine the effect of castration at different weights on feedlot performance and carcass characteristics. Calves were castrated at 70, 230. 320 or 410 kg or left intact. All calves received a 36-mg zeranol implant 6 0 d postweaning and were re-implanted every 56 d for the duration of the trial (196 d). Animals were slaughtered between 14 and 15 mo of age. lntact males gained faster (P<.05) and were more efficient (P<.05) in converting feed to gain than the castrated males. There were no differences (P>.10) in average daily gain (ADG) or feed efficiency (F/G) for males castrated at 70, 230 or 410 kg. However, castration at 320 kg depressed (P<.05) ADG compared with males castrated at 70 kg. Castration at 70 or 230 kg resulted in higher (P<.05) marbling scores than castrating at heavier weights or not castrating. lntact males had the lowest marbling scores, although not significandy lower than castrating a t 320 or 410 kg. lntact males had lower (P<.05) yield grade scores than males castrated at 70 or 230 kg but their yield scores were not different (P>.10) from those castrated at 320 or 410 kg. Tenderness of steaks from animals castrated at 70 kg was greater (P<.10) than for intact males or 4 1 e k g castrates. Tenderness scores for animals castrated a t 230, 320 or 410 kg were not different (P>.10) from the intact males. (