Repository logo

Contraception vaccination for mares and its effects on cyclicity and estrous behavior




Reisenauer, Ashley, author
Bruemmer, Jason, advisor
Coleman, Stephen, committee member
Eckery, Douglas, committee member
Bouma, Jerry, committee member

Journal Title

Journal ISSN

Volume Title


Overpopulation is an issue for wild horses due to limited forage and decreasing water sources. Sterilizing mares without surgical ovariectomy would be cost effective and safer. There are currently no vaccines that cause permanent sterility in mares. Bone Morphogenetic Protein 15 (BMP-15) and Growth Differentiation Factor 9 (GDF-9) are oocyte-specific proteins involved in every stage of follicular development from primordial activation through ovulation. This study investigated the effects of a combination vaccine consisting of these oocyte-specific growth factors, GDF-9 and BMP-15, on mare cyclicity and estrous behavior. We hypothesized that immunization against the combination of these two factors would result in no ovarian cyclicity. Mature, fertile Quarter Horse type mares (n=10/group) each of which had successfully carried a foal within the last 24 months were used. The experiment was conducted from February through September 2018. All mares were vaccinated a total of 5 times starting at week 0, continuing at week 6, 12, 18, and 24. Ten mares received the vaccine consisting of both peptides (GDF-9; SEYFKQFLFPQNEC and BMP-15; QAGSMGSEVLGPSREREGPESNQC) and adjuvant (Seppic Montanide™ Pet Gel A), while control mares received adjuvant alone. All vaccinations were administered IM. Ovarian activity and ovulations were recorded by trans-rectal ultrasonography at least once a week and estrous behaviors were evaluated three days a week by interacting individually with a stallion on a tease rail. Follicle diameters were recorded according to measurements and estrous behavior scored on a 6-point scale (0 = hostile toward stallion – 5 = actively seeking stallion with associated behaviors). Jugular blood samples were collected prior to each weekly palpation, and serum was aspirated for further investigation of the progesterone levels. All control mares cycled normally with ovulations associated with estrus at approximately 3-week intervals. None of the 10 treated mares ovulated or grew a follicle larger than 20 mm during the 8-month experimental period. Mixed estrous behaviors were noted in a few mares throughout the study. Low progesterone levels in serum samples confirmed these findings and are associated with the presence and/or lack of detected corpra lutea. Future research will focus on the active duration of the vaccination to determine the length of effectiveness. This vaccination could serve as a long-term contraceptive in wild horse herd populations.


2019 Summer.
Includes bibliographical references.

Rights Access




Associated Publications