Vaccine Decreases Unwanted Horse Behavior in Study

Vaccination with gonadotropin-releasing hormone (GnRH), a reproductive hormone, might decrease unwanted behavior in stallions and mares, researchers recently reported.

The horses’ owners rated their behavior via a standard questionnaire. Researchers also recorded the results of physical examination, rectal palpation, and rectal ultrasonography.

After two vaccinations with GnRH, decreases in unwanted behavior were observed in 84% of the horses.

The researchers noted significant decreases in the size of mares’ ovaries, as well as the two largest follicles, following vaccination. There was no significant difference in the size of stallions’ testicles before and after vaccination.

The horses tolerated the vaccine well, with only slight local reactions reported in 6.5% of cases.

The study, “The use of a GnRH vaccine in mares and stallions to influence undesirable behavior: A retrospective study of 31 cases,” was published in Schweizer Archiv für Tierheilkunde.