GnRH Vaccine Could Suppress Serum Testosterone in Stallion Mules.

Simple Summary: Stallion mules are infertile but still able to produce testosterone, which influences undesirable behavior. Surgical castration is required to eliminate testosterone synthesis, which results in pain and the risk of postoperative complications. To the best of our knowledge, there are no existing studies regarding immunocastration as an alternative method for surgical castration in mules. The objective of this study was to evaluate whether a gonadotropin-releasing hormone (GnRH) vaccine could be used as a method of immunocastration in stallion mules via the assessment of anti-GnRH antibody concentration, serum testosterone concentration, clinical adverse effects, and changes in the selected behaviors. Intact and unilateral cryptorchid mules received the GnRH vaccine at weeks 0, 4, and 8. The serum testosterone concentrations in GnRH-vaccinated mules were lower than before vaccination from weeks 6 to 14. Subcutaneous edema adjacent to the injection site was observed in intact mules after the second or third vaccination. The stallion mules responded to the GnRH vaccine, resulting in a temporary decrease in serum testosterone. Based on the results of this study, the GnRH vaccine may be administered as a temporary immunocastration method for stallion mules. Stallion mules have been used as working equids in several countries. Aggressiveness under the influence of testosterone results in the necessity for surgical castration before work training. The gonadotropin-releasing hormone (GnRH) vaccine may be an alternative method for immunocastration in mules. The objective of this study was to evaluate the effect of the GnRH vaccine on anti-GnRH antibody concentration, serum testosterone concentration, clinical adverse effects, and behavioral changes in response to receiving selected physical manipulations from humans. Twenty-five mules were separated into three groups: Control-intact, Control-castrated, and Treatment. The Treatment group was further divided according to condition (intact or unilateral cryptorchid) and age. The Treatment group received 195 µg of the GnRH vaccine intramuscularly at weeks 0, 4, and 8. The anti-GnRH antibody concentrations increased at weeks 6 and 10, and then they gradually decreased to baseline at week 24. The Treatment-intact-young group had the highest concentration of anti-GnRH antibody. The serum testosterone concentrations in the Treatment group were lower than before vaccination from weeks 6 to 14. Subcutaneous edema adjacent to the injection site was detected in the Treatment-intact group after booster vaccination. In conclusion, the mules responded to the GnRH vaccine, which could temporarily suppress testosterone for up to 14 weeks. [ABSTRACT FROM AUTHOR]