Ask The Vet: Equine Reproduction

Answered by, Terri Van Wambeke, DVM, Oregon City, Oregon
Courtesy of AAEP

Question: My 6-year-old mare has significant discomfort with ovarian follicles and has responded well to Regumate, which she has been off for 18 months. She is VERY “mareish” but when not in season, solid minded and athletic. I’d like to breed her with a stallion known for his calm and consistent demeanor, outstanding genetics, and overall sound health/mind. Given my mare’s ovarian issues, is there anything I need to be aware of? Is breeding her possibly unsafe and/or unwise? 

Answer: Many mare owners complain of inconsistent work ethic, back pain and changes in attitude during the time of year that their mare is actively cycling. Most of the time there is no specific problem with the reproductive system of the mare that would make it unsafe to breed. Prior to finalizing your decision to breed your mare, you should have a breeding soundness examination performed by a veterinarian experienced with equine reproduction. This examination will answer your questions about the health and fitness of her reproductive tract and alert you to any problems you may encounter along the way. Wishing you all the best with your mare!

Question: My 14 year-old Thoroughbred was easy to get in foal until after her 4th (extremely large) colt. Since then (three years ago), her biopsy graded as IIB and she typically holds fluid post breeding. Are there any new protocols for settling such mares? I’m ready to pull the plug if we’re unsuccessful this year. Is Breed assist an option to improve her chances? Live cover is so harsh and an archaic protocol.

Answer: Endometrial biopsies are graded I, IIA, IIB and III, with each successive progression in biopsy grade holding different statistics for conception and pregnancy loss. As the grade increases, the chances for pregnancy decrease and the amount of inflammation, presence of scar tissue and odds of persistent uterine infection increase. The presence of scar tissue is not treatable but the presence of infection can be addressed, and in some cases may improve the biopsy score. A grade IIB biopsy is indicative of moderate inflammation and scar tissue formation with a 10-50% chance of carrying a foal to term. As you can see this is a fairly wide range.

Additional testing is recommended to give you a better picture of the chances of your mare carrying a foal to term, and would also indicate if any treatment would be necessary prior to breeding. These would include: external genital conformation evaluation, ultrasound exams, speculum exam to look at the integrity of the cervix and check for urine pooling or fecal contamination, uterine culture and cytology and low volume lavage cytology. It is difficult to answer questions about new protocols without knowing the answer to why your mare is having problems. The protocol for treatment or breeding management changes depending on the exact problem the mare is experiencing.

Keep in mind, semen quality and the breeding management of the mare play a large part in any successful breeding program. You may want to consult with a boarded equine theriogenologist or a veterinarian with extensive experience working with mares having breeding difficulties for additional management strategies. It is possible to get some of these mares successfully carrying to term but it requires client commitment and intensive breeding management. Wishing you and your mare a successful outcome!