By Dr. Juan C. Samper, DVM, PHD, DIPL. ACT

Q: I have a 15-year-old mare that I would like to breed. However, she has never had a foal before. Is she too old to breed now? What complications could there be if I decide to go ahead and breed her?

A: Old maiden mares are considered special mares with the possibility of reduced fertility. An old maiden mare is a mare that is older than eight or nine and has never had a foal. However, there are other mares that are in the same category; mares that are bred at the age of two, foal when they are three, and then go into a show career and are not bred again until they are 12 or older behave very similarly. Not all are the same, but they are all at a higher risk of being a problem. 

These mares have cervixes that lose their function, are prone to building fluid in the uterus and developing infections, could have erratic cycles, and most have significant fibrosis (scarring) of the uterus.

It is important to realize that a young maiden mare has a chance of getting pregnant on a per cycle basis of 70 per cent or more, while the old maiden has a chance of 30 to 50 per cent, even though they are both maidens. Mares can be successfully bred until the late teenage years and the risks are the same as any other mare. The primary risk is that it could be more difficult to get pregnant; for pregnancy and foaling, the risks are no different than with other mares.  

Dr. Juan Samper, MSc, PhD, Diplomat ACT, operated JCS Veterinary Reproductive Services in Langley, BC, from 1993-2017. He has consulted with breeders and veterinarians in over 25 countries. He served as the Associate Dean Clinical Affairs at Ross University School of Veterinary Medicine from 2014 to 2017, and is presently the Associate Dean of Students and the University of Florida College of Veterinary Medicine.

This article was originally published in the April 2011 issue of Canadian Horse Journal.

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