Department of Animal Science


Date of this Version



Published in Journal of Animal Science 1987.64:343-347. Copyright © 1987 American Society of Animal Science. Used by permission.


One hundred eighty-eight male calves were randomly assigned to one of five treatments at about 6 wk of age to 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 60 d post-weaning 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. Intact 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. Intact males had the lowest marbling scores, although not significantly lower than castrating at 320 or 410 kg. Intact 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 410- kg castrates. Tenderness scores for animals castrated at 230, 320 or 410 kg were not different (P>.10) from the intact males.