Effectiveness of a New Recombinant antiGnRH Vaccine for Immunocastration in Bulls

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.

Keywords: GnRH antibodies; immunocastration; livestock; meat quality; recombinant vaccine.

Figure 1

Production of anti GnRXG/Q IgG by immunocastrated (IC) Norman × Hereford bulls compared to surgically castrated (SC). The IC group was vaccinated on day 0 and 40 with GnRXG/Q antigen. Data represented as mean ± SEM. Asterisks indicate intergroup significant difference (p-values: * <0.05; ** <0.01; *** <0.001; **** <0.0001).

Figure 2

Average testosterone concentration (ng/mL) for Norman × Hereford bulls surgically castrated (SC) and immunocastrated (IC). Superscripts indicate significant difference (p-value: * < 0.05; **< 0.01).

Figure 3

Individual testosterone concentration (ng/mL) for 10 immunocastrated (IC) Norman × Hereford bulls. Each color represents one bull sampled at various time points pre- and post-vaccination from Day −30 to Day 170.