Mares Can Get Back in Foal Easily Following Induced Abortion

The overall pregnancy rate in this study was 90% and, on average, mares got back in foal about 45 days after abortion.

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Some polo pony breeding facilities report upward of 90% of their foals born in a season are fillies. These aren’t just crazy odds—it’s not uncommon for polo breeders monitor fetal sex and terminate colt pregnancies as soon as the veterinarian detects them (the other option being sex-selection of semen before breeding). But what about the fertility of those aborted mares, many of which are embryo transfer recipient mares expected to produce?

“The reproductive events following induced abortion in mares remain unclear, which may limit veterinarians’ ability to get the mare back in foal in a timely manner,” said Javier J. Aguilar, DVM, PhD, of the Produccion Equina, Facultad de Agronomia y Veterinaria, Universidad Nacional de Rio Cuarto, Argentina, during the 2015 American Association of Equine Practitioners Convention, held Dec. 5-9 in Las Vegas.

In his study of hormone levels, time to ovulation, and pregnancy rates, Aguilar induced abortion in 32 mares carrying colts at Day 65 of gestation.

The most important finding of the study was that 12 of the mares (37.5%) returned to normal cyclicity within 15 days of abortion

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Written by:

Stacey Oke, MSc, DVM, is a practicing veterinarian and freelance medical writer and editor. She is interested in both large and small animals, as well as complementary and alternative medicine. Since 2005, she’s worked as a research consultant for nutritional supplement companies, assisted physicians and veterinarians in publishing research articles and textbooks, and written for a number of educational magazines and websites.

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