Horse-Breeding Dilemma Resolved

Sometimes all it takes to manage mare reproduction problems is working closely with your veterinarian to find the program that works for your mare.

In the January 2011 issue of the Journal, I presented the case of a 15-year old mare with a history of subfertility. A series of tests yielded a final diagnosis of fungal endometritis - the mare had a yeast infection in her uterus. This column will describe the treatment and outcome after the first breeding of the year. Fungal infections of the equine uterus can be difficult to treat and will often recur if all of the organisms aren’t eliminated.

We began therapy in this mare by performing a uterine lavage to eliminate as many yeast organisms, inflammatory cells and debris as possible. White vinegar was added to the saline solution to decrease the pH (i.e. make the lavage fluid more acidic) and help kill the yeast organisms.

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Next, we inserted a small ovule containing the antifungal medication miconazole into the uterus. The only issue with this treatment was deciding who was going to go to the drug store to select the medication from the shelf of feminine hygiene products. Unfortunately, I drew the short straw. We also instituted a course of intrauterine therapy with a second antifungal agent called nystatin, which was dissolved in sterile saline and infused into the mare’s uterus for five consecutive days. It has been our experience that a combination of two antifungal agents rather than one is more likely to resolve fungal endometritis. In addition to the yeast infection, this mare also had bacteria in her uterus. Consequently, we also treated the mare with oral trimethoprim-sulfamethoxasole antibiotics for seven days. A Caslick procedure was performed on the mare to limit re-infection, then she was sent home for the fall and winter. The mare returned this spring to be re-examined and bred. The diagnostic tests were repeated, and the mare was free of infection. She came into heat and when a follicle 36mm in diameter was detected, semen was ordered. Cooled semen arrived the next day, and the mare was inseminated and administered deslorelin to induce ovulation. She pooled a small volume of fluid in her uterus the day after insemination, so her uterus was lavaged and she was administered oxytocin to promote uterine contractions and evacuation of fluid.

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We had to wait two long weeks for the initial pregnancy examination. The entire staff was gathered around the ultrasound machine on the 14-day check. No one even breathed as the examination started. You could have heard a pipette drop. The probe was passed along the middle of the mare's left uterine horn and there it was - a healthy looking embryonic vesicle. The mare was pregnant. A few cheers erupted along with several sighs of relief (mostly mine). The successful outcome in this mare (i.e. a pregnancy) was made possible first by performing tests that provided an accurate diagnosis and second by instituting a sound therapeutic plan. The take-home message is that horse owners should work closely with their veterinarian in the reproductive management of problem mares. A few diagnostic tests could be the key to success.