[The use of a GnRH vaccine in mares and stallions to influence undesirable behavior: a retrospective study of 31 cases].

This research study explored the impact of the Gonadotropin-Releasing Hormone (GnRH) vaccine on the behavior and reproductive function of horses displaying unwanted behaviors. The study found that a GnRH vaccine was able to reduce undesirable behavior in 84% of horses and caused significant reduction in ovarian size in female horses.

Objective of the Study

• The study aimed to evaluate the effects of a GnRH vaccine, Equity, on the behavior and gonadal function in horses displaying unwanted behaviors.
• The researchers used a questionnaire to determine the reasons for treatment and conducted physical examinations, rectal palpation, and rectal ultrasonography to record initial findings.
• The study then compared the results of these examinations and the behaviors of the horses before and after the administration of the GnRH vaccine.

Study Findings

• The research found that the GnRH vaccine caused a reduction of unwanted behavior in 84% of all cases studied.
• Further, in mares, the ovaries were significantly smaller post-vaccination.
• The largest and the second largest follicle on the ovaries were also significantly smaller after vaccination, indicating the vaccine’s effect on the reproductive function.

Effects on Stallions

• In contrast, for stallions, there was no significant difference found in the size of testicles before and after vaccination. This suggests that the vaccine’s effect varies between genders.

Tolerance and Side Effects

• The study noted that the vaccine was generally well tolerated in horses. However, minor local adverse reactions were reported in 6.5% of all cases. This indicates the vaccine is largely safe but may cause occasional mild side effects.