Case Study: Effect of injectable castration regimen on beef bull calves

Castration is performed on bull calves to reduce aggressiveness and sexual activity, improve worker safety, prevent unwanted breeding, and improve meat quality. The objective of this study was to evaluate the effect of a zinc solution as an injectable castration method to bull calves before weaning. Crossbred bull calves (n = 31; BW = 115 ± 26.4 kg; age = 119 ± 18.4 d) were allocated to treatments by BW and birth date. Twenty-seven bull calves were allocated to 3 injectable castration treatments (n = 9 calves per injectable castration treatment) to reflect 3 dosage levels of the zinc solution (Calviex, Cowboy Animal Health LLC, Plano, TX). On d 0, a single injection of the zinc solution was placed in each testicle. Two bull calves were castrated surgically, and 2 bull calves were left intact until weaning. Calves were weighed on d 0 and on 28-d intervals until they were weaned on d 122. Blood samples and scrotal measurements were obtained on d 0, 28, 56, 83, and 122. There were no effects (P ≥ 0.67) of Zn solution concentration on BW. A main effect of treatment (P = 0.005) showed intact bulls had greater (P < 0.001, orthogonal contrast of intact vs. castrated) serum testosterone concentrations than bulls castrated with any method. At weaning, there were no differences in growth, serum testosterone, or scrotal thickness due to the concentration of Zn solution used, and the injectable castration method resulted in similar serum testosterone concentrations compared with surgical castration, hence, resulting in successful castration.