Effects of a commercial canine gonadotropin releasing hormone vaccine on estrus suppression and estrous behavior in mares.

This research investigated the potential of using a canine vaccine to suppress estrous cycles in mares. It found that the vaccine was able to effectively decrease unwanted estrous behaviors and stop ovarian activity.

Research Methodology

The study was conducted in two parts.

• In the first experiment, 6 mares were immunized with a canine gonadotropin releasing hormone (GnRH) vaccine twice, four weeks apart. This group was compared with a control group of 5 mares that received a control diluent. The researchers carried out transrectal ultrasonographic examinations of the mares’ reproductive tracts three times a week for 40 weeks after the mares had been vaccinated. Blood samples were collected weekly to measure GnRH antibody titer and progesterone concentration.
• In the second experiment, 12 privately-owned mares were immunized twice, again four weeks apart. Here, the blood samples were collected prior to each vaccination as well as 12 and 20 weeks after the initial treatment. Their reproductive tracts were examined by ultrasound 12 weeks after the first vaccination.

Results and Findings

• In both experiments the mares that were vaccinated showed a response to the GnRH vaccine. The mares developed a GnRH antibody titer, which suggests an immunological response to vaccination.
• Progesterone concentrations significantly dropped in both groups of mares that were vaccinated, when compared to the control group. This implied a cessation of ovarian activity, as progesterone is a hormone produced by the ovaries that indicates reproductive activity.
• Mares in the second experiment maintained these low progesterone levels throughout the duration of the study, which suggests that the effects of the vaccine were sustained over time.
• The owners of the vaccinated mares in the second experiment also reported a noticeable decrease in unwanted estrous behaviors. It implies a behavioral change related to the cessation of estrous cycles due to the vaccine.

Conclusions

In conclusion, vaccination with a canine GnRH vaccine appears to be an effective method for suppressing estrus and the associated unwanted behaviors in mares. The cessation of ovarian activity indicated by the decreased progesterone and the behavioral changes observed suggest that this could be a promising technique for managing estrus in mares.