Effects of Late Castration and Zeranol on Feedlot Performance and Carcass Characteristics of Bovine Males1,2

Abstract

The effects of surgical castration at 13 mo of age and zeranol, implanted in either the ear or scrotum, were evaluated in 231 bovine males representing seven breed groups. During a 103-d feeding period, males were penned by treatment with 28 to 30 males/pen and two pens/treatment. All breed groups were represented in each pen. Intact males gained 24% faster (P<.05) and consumed 22% less (P<.01) feed/unit of gain than males castrated at 13 mo of age. Zeranol implants did not have a significant effect on average daily gain, feed efficiency or carcass traits. Late castration reduced (P<.01) carcass weight, estimated cutability (percentage), and estimated retail product (percentage). Dressing percentage and scores for carcass secondary sex characteristics, marbling, final maturity, lean color and lean texture were not affected significantly by late castration or zeranol treatment. Secondary sex characteristic scores for males castrated at 13 mo of age decreased during the experiment and on d 85 were lower (P<.01) than observed in intact males. We conclude that intact males are superior to males castrated at 13 mo of age in the economically important traits of rate of gain, feed efficiency and yield of edible product. Copyright © 1983. American Society of Animal Science . Copyright 1983 by American Society of Animal Science.