Suppression of behavioural and physiological oestrus in the mare by vaccination against GnRH
Article first published online: 14 FEB 2007
Australian Veterinary Journal
Volume 85, Issue 1-2, pages 39–45, January 2007
How to Cite
Elhay, M., Newbold, A., Britton, A., Turley, P., Dowsett, K. and Walker, J. (2007), Suppression of behavioural and physiological oestrus in the mare by vaccination against GnRH. Australian Veterinary Journal, 85: 39–45. doi: 10.1111/j.1751-0813.2006.00092.x
- Issue published online: 14 FEB 2007
- Article first published online: 14 FEB 2007
- (Accepted for publication 1 November 2006)
- gonadotrophin releasing hormone;
- equine reproduction
Objective To examine the immunogenicity of an equine immunocontraceptive vaccine and its efficacy in controlling hormone-related behaviour.
Design A total of 24 mares at two sites in Australia were vaccinated with an immunocontraceptive vaccine comprising gonadotrophin releasing hormone (GnRH) conjugated to a carrier protein in immunostimulating complex as an adjuvant. Twelve animals at each site received a placebo of adjuvant alone and served as controls for seasonal oestrus, hormonal and behaviour patterns. Animals were observed for injection site reactions, ovarian and follicular activity, and serum levels of antibody, 17β-oestradiol and progesterone in the weeks following vaccination. Mares were also examined for oestrous behaviour by teasing with a stallion.
Results All mares responded to vaccination. Two weeks following the second vaccination there was a peak in antibody response to GnRH that declined gradually over the following weeks. Commensurate with the elevated anti-GnRH antibody there was a marked effect on ovarian activity with a reduction in 17β-oestradiol and progesterone levels in the 24 vaccinated mares. There was also a reduction of oestrus-related behaviour as determined by a teaser stallion. This effect lasted a minimum of 3 months and correlated with the initial level of antibody response.
Conclusion Following a conventional two-dose immunisation regime this commercially available equine immunocontraceptive vaccine was effective at inhibiting oestrous behaviour for at least 3 months. This vaccine has a high level of safety since there were no significant local reactions nor were there any adverse systemic responses to vaccination.