Effects of Injectable Castration Regimen on Beef Bull Calves Ball, J. et al. University of Arkansas, Division of Agriculture, Department of Animal Science Arkansas Animal Science Department Report, Arkansas Agricultural Experiment Station Research Series 638:9-10 (December 2016) Husbandry practices in the beef industry that are associated with pain, discomfort and distress include castration, dehorning and branding. It has been estimated there are approximately 15 million castration procedures performed in the United States annually to reduce aggressiveness and sexual activity, prevent unwanted breeding and improve the quality of meat. In Arkansas, only 17 percent of male calves sold in livestock auctions weighing between 300 and 550 pounds were already castrated; and of the bulls placed on feed in feedlots in 2008, roughly 91 percent were castrated, predominantly by band castration (64 percent) or surgical castration (19 percent). Economically, castration post-weaning affects profitability by decreasing average daily gain and increasing susceptibility to bovine respiratory disease. Currently, no commercially available injection sterilization method exists for beef cattle in the United States, although there has been a zinc solution utilized in other species. An injectable sterilization method could be an alternative castration method that could potentially reduce pain, stress and performance loss and minimize the prevalence of bovine respiratory disease. Therefore, this research project was designed to evaluate an injectable zinc solution at three dosage levels for the efficacy of castration in beef bull calves prior to weaning on weight gain, testosterone production and testicle atrophy. • Thirty-one bull calves were allocated to treatments by body weight (average BW = 284 ± 55 pounds) and birthdate. Twenty-seven bull calves were allocated to three injectable castration treatments reflecting three levels of dosage concentration of a zinc-based solution and administered as 1 milliliter (1 cc equivalent) of zinc solution to each testicle. Two bull calves were castrated using a surgical technique while two bull calves were left intact until the termination of the study at weaning. • Calves were weighed with no further shrink on 28-day intervals and weaned from dams on September 30. At each subsequent 28-day interim weight collection and at the end of the study on October 3, calves were bled via jugular venipuncture to determine serum testosterone. On the same day, the thicknesses of the right testicle and scrotum were measured. • There were no effects of castration or castration method on body weight or preweaning average daily gain. Over the course of the experiment, mean average daily gain was nearly or slightly above 2 pounds per day for the initial two 28-day intervals (1.95 ± 0.15 and 2.01 ± 0.18 pound per day, for periods 1 and 2, respectively), yet declined to 1.63 ± 0.17 pound per day in period 3 and to 0.33 ± 0.15 pound per day in the final period before weaning. The decline in performance during the late summer is due to seasonal deterioration in forage quality and was not related to treatments imposed. Bodyweight at weaning averaged 445 ± 30 pounds. • There were no differences in scrotal thickness, growth performance or testosterone concentrations regardless of the dosage concentration of zinc. The injectable castration method resulted in serum testosterone concentrations similar to calves that had been surgically castrated. Source: Beef Cattle Research Update, University of Arkansas