Dose-dependent effects of a recombinant gonadotropin-releasing hormone vaccine on reproductive function and growth...

This study aimed to develop a recombinant gonadotropin-releasing hormone (GnRH) vaccine and to investigate the effects of different immunization doses on immunocastration efficacy and growth performance in male goats; thererby providing an animal welfare-friendly alternative to surgical castration (SC).

Forty male goats were randomly assigned to four groups (n = 10 per group): the saline-injected control (NC), SC, low-dose vaccine (LD), and high-dose vaccine (HD). The vaccine was given in accordance with a regular immunization protocol. Anti-GnRH antibody titers, serum testosterone concentrations, libido scores, histological characteristics of testicular tissues, and growth performance were measured to assess immunocastration efficacy.

Both LD and HD groups exhibited significantly higher anti-GnRH antibody titers than the NC group (p<0.01). Serum testosterone concentrations and libido scores were markedly reduced in the immunized groups (p<0.01), indicating effective suppression of reproductive function. Histological and quantitative analyses demonstrated pronounced testicular atrophy in immunocastrated goats, characterized by a significant reduction in seminiferous tubule diameter and spermatogenic cell number, as well as the absence of spermatozoa within the lumen. Although only limited time points showed significant differences between the two immunization doses, the overall immunocastration efficacy of the low- and high-dose regimens was largely comparable, with the low-dose group exhibiting slightly stronger suppression in certain parameters or time points. Additionally, immunocastrated goats had significantly higher body weight and weight gain compared to surgically castrated goats (p<0.01), while differences with the NC group were not significant (p>0.05).

The recombinant GnRH vaccine effectively suppresses reproductive function in male goats. Compared with SC, immunocastration was associated with improved growth performance, while no significant differences were observed relative to intact animals. These findings support immunocastration as a non-invasive and animal-friendly alternative to SC in livestock production.