This time of year, most pregnant broodmares are out to pasture, quietly “gestating” until their expected foaling dates in the spring. But that doesn’t mean you can just assume that they’re OK.
Here’s a checklist for managing mares at this stage of their pregnancies:
1. Every year, up to 15 percent of broodmares that were checked safe in foal at 45 to 60 days of pregnancy lose their pregnancies prior to foaling season. So have your bred mares rechecked when they get one of their EHV-1 vaccinations to confirm that their pregnancy is progressing normally. By the time a mare owner figures out that the mare has lost her pregnancy, there is not sufficient time to determine the cause, initiate treatment to correct the problem and rebreed the mare.
2. Broodmares in a 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 pregnant mare should have a body condition score of 6 or better, should have a level back, slight fat cover over the ribs, and fat should be evident along the sides of the neck and behind the shoulder. We don’t want the mare fat because fat mares tend to produce less milk than moderately fleshy mares, so their foals gain less weight. In the last trimester, the unborn foal’s growth rapidly accelerates, as does the mare’s nutritional requirements, so increase her feed ration accordingly. On average, a healthy mare in good flesh will gain 10-12 percent of her original body weight during pregnancy.
3. Make sure she is well vaccinated against tetanus, eastern and western encephalomyelitis, West Nile virus and rabies four to six weeks prior to foaling to provide her foal the best-quality colostrum possible.
4. Pregnant mares should also receive rhinopneumonitis vaccinations during mid- to late pregnancy. A typical rhino vaccination schedule is to vaccinate pregnant mares during their fifth, seventh and ninth month of pregnancy. An alternate program is to vaccinate every other month once the mare becomes pregnant. Other common vaccinations that may be necessary include Strep. equi (strangles), Potomac Horse Fever and influenza. Your local veterinarian is the best source of information on a good vaccination program for your pregnant mare.
5. If your broodmares are on tall fescue pasture or are receiving fescue hay, remove them from fescue pastures six to eight weeks prior to their foaling date. If this is not possible, provide them with plenty of good-quality non-fescue hay the last few months of pregnancy and consider administering daily the paste drug domperidone, which helps counteract the effects of fescue toxicosis, the last 25 to 30 days prior to foaling. Because an affected mare, even following preventative treatment, might not produce adequate amounts of colostrum, it’s a good idea to have some frozen colostrum on hand for the newborn foal.
6. Inventory foaling and breeding-related supplies and equipment to ensure that needed items are on hand. Develop an emergency plan with your veterinarian for your foaling mares and review the three stages of the normal foaling process to ensure that you are able to recognize problems early enough to get help. Place emergency phone numbers near the phone in your barn and evaluate foaling areas to make sure there are no hazards that may injure the mare or newborn foal.
by Dr. Tom Lenz