Effects of immunization against bone morphogenetic protein-15 and growth differentiation factor-9 on ovarian function in mares

Authors

Kelli A. Davis, Colorado State University - Fort Collins
Kristin M. Klohonatz, Colorado State University - Fort Collins
Darcy S.O. Mora, USDA National Wildlife Research Center
Hannah M. Twenter, Colorado State University - Fort Collins
Peter E. Graham, Colorado State University - Fort Collins
Pablo Pinedo, Colorado State University - Fort Collins
Douglas C. Eckery, USDA National Wildlife Research CenterFollow
Jason E. Bruemmer, Colorado State University - Fort CollinsFollow

Document Type

Article

Date of this Version

2018

Citation

Animal Reproduction Science 192 (2018) 69–77

Comments

© 2018 Elsevier B.V.

This document is a U.S. government work and is not subject to copyright in the United States.

https://doi.org/10.1016/j.anireprosci.2018.02.015

Abstract

Currently there is no contraceptive vaccine that can cause permanent sterility in mares. This study investigates the effect of vaccination against oocyte-specific growth factors, Bone Morphogenetic Protein 15 (BMP-15) and Growth Differentiation Factor 9 (GDF-9), on ovarian function of mares. It was hypothesized that immunization against these growth factors would prevent ovulation and/or accelerate depletion of the oocyte reserve. For this study, 30 mares were randomly assigned to three groups (n=10/group) and vaccinated with BMP-15 or GDF-9 peptides conjugated to KLH and adjuvant, or a control of phosphate buffered saline and adjuvant. Horses received vaccinations at weeks 0, 6, 12, and 18. Ovarian activity and estrous behavior were evaluated 3 days a week via ultrasonography and interaction with a stallion. The study was initiated on March1, 2016. Upon evaluation of ovulation rate, the GDF-9 group did not have a difference (P=0.66) in ovulation rate when compared to controls (10.8 and 10.0 ovulations, respectively), but the number of ovulations in the BMP-15 group was less (P=0.02; 4.9 ovulations). Average follicle size prior to ovulation was less (P < 0.0001) in both treatment groups compared to controls. Estrous behavior was altered in both the BMP-15 and GDF-9 groups compared to controls after the second vaccination (P=0.05 and 0.03, respectively). Although further research is required to determine the continued effects of vaccination against GDF-9 on ovulation rates, these results indicate that vaccination against BMP-15 and GDF-9 could serve as a contraceptive in wild horse populations.