Equine Matters Spring 2019

13 Equine Matters Spring 2019 Infertility Infertility - why is my mare not in foal? Andrea Kilduff-Taylor MA VetMB MRCVS 608 Equine & Farm One of the great pleasures of horse ownership can be breeding from your own mare. Imagine breeding a foal with your mare’s lovely temperament but with improvements in conformation contributed by the stallion. As our horse population is living longer, and therefore competing for longer, we often find ourselves wanting to breed from older mares. Unfortunately the fertility of a mare starts to decline quite early, at around 15 years. Here are some of the relevant factors: l Sagging of the uterus and vulva l Tight cervix (if maiden mare) l Decreased egg viability l Uterine cysts l Degeneration of the uterine lining However, sometimes things aren’t so simple and we can be left frustrated when we can’t get a mare in foal. This article will explore some of the reasons why we can struggle to achieve a successful pregnancy in a mare and what we can do about it. Age Some of these factors cannot be addressed and sometimes we have to concede that we cannot breed from the mare. Endoscopy (where a camera is passed into the uterus) allows us to remove uterine cysts and mares can often go on to be bred successfully if this is their only issue. If a biopsy of the uterine lining is taken then we can assess it under the microscope and decide on the likelihood of pregnancy. If having a foal from this mare is very important, in some cases treatment can be attempted to improve the uterine lining. When planning for the future, it is beneficial to think about breeding from mares when they are young adults. Technology such as embryo transfer can allow us to have our cake and eat it, as we can breed from competition mares without needing them to carry their own foals. Infection and inflammation Uterine infections and inflammation create a poor environment for an embryo. These issues can arise due to entry of bacteria into the uterus during breeding, or due to problems with the seal between the uterus and the outside. l Vulva: Older mares and sometimes very fit (or underweight) younger mares can have a sunken vulva (see Figure 1). This means the vulva doesn’t seal properly and air and faeces can be sucked in. l Cervix: This is a very changeable structure which opens when the mare is in season and closes between seasons. This opening up allows drainage of fluid from the uterus after breeding. Some older maiden mares (mares which haven’t been bred before) have a tight cervix which doesn’t open properly and so traps fluid in the uterus. l Sagging of the uterus often happens in older mares and can cause fluid to pool rather than draining out. l Urine pooling is also related to sagging of the uterus - urine goes into the vagina instead of exiting, causing inflammation and bacterial contamination. Figure 1: An underweight mare with a sunken vulva. Note the anus is positioned further in than the vulva