05/10/2026
BROODMARE CHECKS
By Thomas R. Lenz, D.V.M., M.S.
NOW THAT COLD WEATHER HAS MOVED IN, most broodmares are out to pasture gestating until their expected foaling dates next spring. Unfortunately, each year up to 15 percent of broodmares that were checked safe in foal at 45-60 days lose their pregnancies by late fall. It's a good idea this time of year to recheck all of your mares by ultrasound or palpation to confirm that their pregnancy is progressing normally.
Too often, as mare owners, you don't know your mare lost her pregnancy until she doesn't foal in the spring. This is often so late in the breeding season that there is not sufficient time for your veterinarian to determine the cause of the lost pregnancy, treat and cor-rect the problem, and rebreed the mare. You lose an entire year.
Once your mare is confirmed safe in foal, there are a number of things that you can do to protect your investment and improve the odds of producing a healthy foal next spring. Many mares drop in body condition at the start of fall and winter because of decreased availability of good pasture and the onset of cold weather. The demands on the mare by the fetus won't require an increase in feed until the last one-third of pregnancy, but the energy required to keep warm will increase.
Research has shown that broodmares in moderate to fleshy condition will be better prepared to provide adequate milk for their growing foals and will breed back quicker than thin mares. A mare should have at least a body condition score 6. She should have a level back, slight fat cover over the ribs and fat should be evident along the sides of her neck and behind her shoulder. On the other hand, a mare should not be rolling fat because fat mares tend to produce less milk than moderately fleshy mares, and their foals gain less weight.
In the last trimester, the unborn foal's growth accelerates, as do the mare's nutritional requirements.
Her feed ration should increase accordingly. On average, a healthy mare in good flesh will gain 9-12 percent of her original body weight during pregnancy. For example, an 1,100-pound mare should gain roughly 100-130 pounds during the course of her pregnancy. She should gain roughly two-thirds of the weight in the final three months prior to foaling.
Develop a Plan
Once your mare is in good flesh, check her vaccination and deworming schedule.
Deworming and vaccination sched-ules vary according to your region, but a general recommendation is that mares should be dewormed every 60 days throughout their pregnancy. They should be vaccinated for tetanus and encephalomyelitis (sleeping sickness) four to six weeks prior to the expected foaling date.
Traditionally, breeders have only been concerned about eastern and western sleeping sickness, but with the speed that West Nile Virus is spreading across the country, every mare should be vaccinated against it prior to warm weather next spring. In addition, pregnant mares should receive rhinopneumonitis (thi-no) vaccinations during mid-to-late pregnancy.
A typical rhino vaccination schedule is to vaccinate pregnant mares during their fifth, seventh and ninth months of pregnancy. An alternate program is to vaccinate every other month once the mare becomes pregnant. Other common vaccinations that might be necessary in some parts of the country include strangles, Potomac Horse Fever, rabies and influenza. Contact your local veterinarian about a good vaccination program for your area of the country.
Other Concerns
If your mare is on her way to a broodmare farm or across state lines to be bred, now is a good time to ask your veterinarian to draw blood for a Coggins test for equine infectious anemia. EIA is a non-treatable, often fatal disease that can only be managed by preventing exposure to infected horses. A negative Coggins test and health certificate are required by most states and broodmare farms. Too often, mare owners are not aware of this requirement and learn of it only when they are ready to ship their mare.
Make decisions now regarding management of your mares if they are on tall fescue pasture or receiving fescue hay. Fescue is a common pasture in most parts of the country and is relatively harmless to adult horses. Unfortunately, it is frequently infected with an endophyte fungus (Festuca arundinacea) that causes prolonged gestation, lack of milk production and foaling problems in pregnant mares.
Remove pregnant mares from fescue pastures 60-90 days prior to their anticipated foaling date. If removing the mares isn't possible, provide them with plenty of good-quality fescue hay the last few months of pregnancy and consider administering domperidone daily. Domperidone helps counteract the effects of fescue toxicosis during the last 25-30 days prior to foaling. Because an affected mare, even following preventive treatment, might not produce adequate amounts of colostrum, it's a good idea to have some frozen colostrum on hand for the newborn foal.
