Effect of a single or two doses of an anti-GnRH vaccine on testicle morpho-functional characteristics in Nelore bulls

Emanuel M Doroteu,Pedro M O Pedroso,Jair A Ferreira Junior,Rodrigo A Oliveira,Joao H M Viana,Juliana T A Macedo

doi:10.1007/s11250-021-02600-x

Emanuel M Doroteu, Pedro M O Pedroso + Show 4 more

Open Access

https://doi.org/10.1007/s11250-021-02600-x

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Abstract

The aim of this study was to compare testicle morpho-functional characteristics in bulls undergoing a single or two immunizations against GnRH. Nelore (Bos taurus indicus) bulls were randomly allocated into three experimental groups: G1 (n=12), a single 400 μg dose of anti-GnRH vaccine on day 0; G2 (n=11), a first 400 μg dose of anti-GnRH vaccine on day 0 followed by a second (boost) dose 30 days later; and control group (CG, n=12), 1 mL saline 0.9% at day 0. Every 30 days, from day 0 until slaughter at day 90, the bulls were weighed and underwent testicular biometry, semen collection and analysis, and blood sample collection for testosterone measurement. Immediately after slaughter, the testicles were removed and transport at 15°C to the laboratory for histopathological analysis. There was a decrease in testicular height (P=0.0476), width (P=0.0021), and in scrotal circumference (P=0.0001), after either a single (G1) or two (G2) immunizations against GnRH. Both G1 and G2 had lower testosterone concentrations than CG from day 60 on (P<0.01), but in G2, it was also lower than in G1 at day 90 (P=0.0006). All sperm parameters were affected by active immunization against GnRH (P<0.05), and in G2, averages were lesser (P<0.05) than in G1 from day 60 on. No signs of seminiferous tubule degeneration were found in any sample from the CG, contrasting with 75.0% and 100.0% of the samples from G1 and G2, respectively. In summary, immunocastration affected testicle morpho-functional characteristics in bulls in a time- and dose-dependent way.

Highlights

Castration of male cattle is a practice adopted worldwide by the beef industry
All sperm parameters were affected by active immunization against GnRH and decreased over time (Fig. 2a to e; P
Sperm concentration (Fig. 2a) in G2 was lesser than in G1, and both were lesser than control group (CG) from day 30 (P

Summary

Introduction

The surgical removal of the testicles (orchiectomy) impairs the production of testosterone and reduces typical male aggressive behavior, attenuates stress, prevents accidents resulting from mounting acts, and facilitates cattle handling in confinement. It may improve meat marble and tenderness (Marti et al 2013) while reducing fights in the pre-slaughter. Castrated steers undergo inflammation (Marti et al 2017) and long wound healing periods (Mintline et al 2014), causing extra expenses with labor and medication. There is an increasing public concern about animal welfare, and a negative perception on surgical castration when performed without pain control (Wolf et al 2016; Lemos Teixeira et al 2018)

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