Effectiveness of a New Recombinant antiGnRH Vaccine for Immunocastration in Bulls

SIMPLE SUMMARY: Castration of males is a common procedure in cattle production. Surgical procedures are most commonly used, but there is an increasing interest in non-invasive alternatives to avoid risk of infection, bleeding, pain, stress and to improve animal welfare. Immunization against gonadotropin-releasing hormone is currently being used in livestock, but there is only one commercially available vaccine for cattle and results regarding the number of doses needed to maintain castration are variable. The efficacy, safety, and production parameters of a new antigen for immunocastration in bulls was assessed. Results showed that two doses of the vaccine to 40 10-month-old bulls achieved testosterone suppression below productive performance. Live weight at slaughter and carcass yield was greater in immunized animals than in surgically castrated cattle. Castration effects of the vaccine were maintained until the end of the trial at 24 weeks. ABSTRACT: Castration by surgical techniques is common in livestock; however, post-surgery complications and concerns for animal wellbeing have created a need for new non-invasive alternatives. The objective of this study was to evaluate immunocastration in bulls using antigen GnRX G/Q; a recombinant peptide proved to be effective in laboratory and companion animals. A nine-month trial with 80 9-month-old Normand x Hereford bulls, kept in a pastured system, was conducted. The herd was divided in half with 40 bulls surgically castrated (SC) and 40 castrated by immunization against GnRH (IC). The antigen was injected on days 0 and 40 of the experiment. After the second dose, the IC group had elevated GnRH antibodies and decreased testosterone levels (below 5 ng/mL) that were maintained for 23 weeks. At slaughter on day 190, the immunocastrated group obtained a higher weight, hot carcass, and dressing percentage than the SC group. There was no difference in pH, color of meat, fat coverage, cooking loss, or tenderness between groups. The bulls showed no inflammatory reaction at the injection site or adverse side effects from the vaccine. Our results demonstrate that immunocastration with GnRX G/Q is an efficient and safe alternative to surgical castration in livestock. Additional work evaluating antigen effects over a longer period is needed to validate commercial viability.