AAEP Annual Convention Orlando 2007
Back to Table of Contents
Add to My Library
Comments
Share:

GnRF Immunization in Mares: Ovarian Function, Return to Cycling, and Fertility

Author(s):
Card C.,
Raz T.,
LeHeiget R. and
Sibert G.
In: AAEP Annual Convention - Orlando, 2007 by American Association of Equine Practitioners
Updated:
DEC 05, 2007
Languages:
Back to Table of Contents
Add to My Library

Gonadotrophin-releasing factor (GnRF) immunization provides effective temporary control of estrous cycling and fertility in mares.

1. Introduction

Gonadotrophin-releasing factor (GnRF) immunization suppresses luteinizing hormone and follicle stimulation hormone, causing immune-mediated anestrus in mares. The objective of the study was to characterize responses to the GnRF vaccinea on estrous cycling and fertility in multiparous mares.

2. Materials and Methods

A randomized, blinded, placebo-controlled field study was performed. By July 2004, 82 foaling mares, mean age of 6.0 ± 2.7 (standard deviation) yrs, were determined to be cycling, randomized to two groups (n = 61, GnRF vaccine [a] ; n = 21, placebo), and treated twice 4 wks apart. All mares received ultrasound examinations every 2 wks until December 2004. In 2005, all mares underwent repeated ultrasound examinations before and after pasture breeding. Mares barren in 2005 were similarly examined and pasture bred in 2006.

3. Results

In 2004, 4 wks after the second dose, 98% of immunized mares were anestrus or transitional, compared with 15% of placebo mares. Vaccinates ceased cycling for the remainder of breeding season, but placebo mares cycled normally, with seasonal anestrus reaching 90% by early December. After the 2004 GnRF vaccination, 100% of placebo and 88% of vaccinated mares were detected cycling in the 2005 breeding season, and 98% of the vaccinated group were cycling by 2006. In 2005, 100% of the placebo group and 75% of the vaccinated mares were pregnant after pasture exposure, and by 2006, 90% of the vaccinated group had confirmed pregnancies. Live foal rates in bred mares were 90% in the placebo group and 95% in the vaccinated group.

4. Discussion

Immunization with the GnRF vaccine [a] caused immune anestrus by rapidly curtailing estrus cycles in 60/61 (98%) of mares for the remainder of the 2004 breeding season. Immune anestrus was temporary, with 88% of the vaccinated group cycling in 2005 and 98% by 2006. Pregnancy rates (PRs) in pasture-exposed mares were high (placebo mares, 100% PR in 2005; vaccinated mares, 75% PR in 2005 and 90% PR by 2006). Live foal rates in immunized and placebo mares were similar.

This study was financed by Pfizer Animal Health.

Footnote

[a] EQUITY, Pfizer Animal Health, Parkville, Victoria 3052, Australia.

Back to Table of Contents
Add to My Library

Ask the author

0 comments
Submit

How to reference this publication (Harvard system)?

Card, C. et al. (2007) “GnRF Immunization in Mares: Ovarian Function, Return to Cycling, and Fertility”, AAEP Annual Convention - Orlando, 2007. Available at: https://www.ivis.org/library/aaep/aaep-annual-convention-orlando-2007/gnrf-immunization-mares-ovarian-function-return-to-cycling-and-fertility (Accessed: 04 October 2023).

Author(s)

Copyright Statement

© All text and images in this publication are copyright protected and cannot be reproduced or copied in any way.

Readers also viewed these publications

Provided by:

The AAEP represents nearly 9,300 veterinarians and veterinary students in 61 countries who cover a broad range of equine disciplines, breeds and associations. The AAEP is primary resource for education, professional development and ethical standards for its members. The AAEP and its members are recognized as the voice and authority for the health and welfare of the horse. The AAEP conducts regular strategic planning every three to four years in order to establish priorities and set direction for the association over the current planning horizon.  The AAEP is a respected source of information for influencing public policy.  

Learn more
Back To Top