Oklahoma-Farm-and-Ranch_531099

OKFR 16 | JUNE 2026 B By the time the June issue reaches readers, the regular breeding season is winding down for many horse owners. Some mares are already con- rmed in foal, some breeding decisions have been pushed aside for another year and some owners are already thinking ahead to next season. For those with an older mare they hope to breed, that early planning can make a real di erence. Older mares can still produce foals, but they may need more help than younger mares. Age a ects the reproductive system, and those changes can make it harder for a mare to become pregnant, stay pregnant or carry a healthy foal to term. That does not mean every older mare is a poor candidate for breeding. It does mean owners should go into the process with realistic ex- pectations and a good veterinar- ian involved from the beginning. A mare’s reproductive age does not always match her num- ber of birthdays. Some mares in their mid-to-late teens settle easily and carry foals without much trouble. Others begin having problems earlier. Past reproductive history matters. A mare that has had regular foals may be di erent from an older maiden mare that spent most of her life showing, racing, working or sitting open. Health, body condition, uterine health and conformation all play a role. One of the main challenges with older mares is egg qual- ity. As mares age, their eggs age, too. Older eggs are more likely to have abnormalities that prevent fertilization, stop early embryo development or lead to early pregnancy loss. Even when breeding is timed well and the stallion has good fertility, the mare may not settle because the By Ann Asher Breeding the Older Mare egg itself is no longer as viable as it once was. The uterus also changes with age. The lining of the uterus, called the endometrium, can become less healthy and less able to support pregnancy. Over time, some mares develop bro- sis or scarring within the uterus. This can interfere with the pla- centa’s ability to develop and support a growing fetus. A mare may get pregnant early, but then lose the pregnancy because the uterus cannot maintain it. Older maiden mares can face an additional problem. When a mare cycles, it is normal for some uid to be present in the uterus. A healthy reproductive tract clears that uid through uterine contractions and cervi- cal relaxation. In some older mares, espe- cially those that have never had a foal, the cervix may not relax well enough. Fluid can build up and remain in the uterus after breeding. That uid can damage sperm, interfere with an embryo and increase the risk of infection or in ammation. Post-breeding inflamma- tion is another concern. All mares experience some uterine inflammation after breeding, but most clear it within a rea- sonable amount of time. Older mares may not clear it well. This can leave the uterus in a poor environment for pregnancy. A veterinarian may recommend uterine lavage, medication or other treatment after breeding to help the mare clear uid and in ammation. External conformation can also affect fertility. As some mares age, especially taller, thinner mares or mares that have had multiple foals, the reproductive tract may tilt in a way that allows manure or air to contaminate the vulva and vagina. Poor vulvar conformation can increase the risk of uterine infec- tion. In some cases, a veterinar- ian may recommend a Caslick’s procedure to help protect the reproductive tract. Because so many factors can be involved, an older mare should have a breeding sound- ness exam before the next sea- son begins. This may include a physical exam, reproductive ultrasound, uterine culture, cytology and possibly a uterine biopsy. These tools help de- termine whether the mare has infection, inflammation, fluid retention, poor uterine health or other issues that need to be addressed before breeding. Timing is also important. With an older mare, it is usu- ally better to start early in the season rather than waiting until late. More cycles give the veterinarian more chances to manage the mare properly. Early planning also allows time to treat infection, improve body Age a ects the reproductive system, but that does not mean every older mare is a poor candidate for breeding. (Crourtesy photo)