Mares are pregnant a long time – eleven months and ten days.  After waiting that long, it is important to do everything possible to have a healthy foal.  Good nutrition is important as well as deworming and vaccinating the mare during her pregnancy. 

The journey starts when the mare gets bred.  The uterus needs to be healthy, the mare's weight should be appropriate, not a body score of  8 or 9 and she should be able to move around well.  Breeding a mare with severe arthritis or founder is risky as she will gain a large amount of weight during her pregnancy and she needs to be comfortable both during her pregnancy and once she has a foal running around.  

Mares can get bred live cover either by being turned out with the stallion or while being covered in hand.  Artificial insemination has also been used very successfully and the mare doesn't need to be transported to the stallion.  Other options include the use of frozen semen as well as embryo transfer.   

The next step would be pregnancy diagnosis.  We recommend ultrasounding the mare early in pregnancy so that twins can be diagnosed and treated if found.  Mares do not do well with twins as the uterus is just not big enough to carry two foals.  Usually twins are aborted late in pregnancy or, if the mare is able to carry them full term, the twins are small with very crooked legs.  One healthy foal is much better than two with problems.  Thoroughbreds and Belgians are the most likely breeds to have twins with the incidence in Thoroughbreds being the highest.  Ponies are the least likely to have twins.  The mare's ovaries releasing two eggs during the same cycle can result in twins.   

The embryo is the most fragile during the first 30 days.  Ten to fifteen percent of embryos are reabsorbed during this time period which may explain some of the irregular cycling seen in mares.  This is why we recommend ultrasounding the mare twice, once early on to determine if she is bred and at 45 days to make sure she has made it through the critical early days.  The fall is another good time to confirm a pregnancy to make sure that the weight that the mare is gaining over the winter is from the foal and not just fat. 

A regular deworming schedule should be followed during the pregnancy using products which are safe for pregnant mares.  The mare should be on good nutrition during her pregnancy but she should not get too fat.  If the mare is being fed a well balanced formulation, it is not necessary to add supplements at all.  Regular exercise is helpful which can be riding during the first two trimesters and just turn-out during the last few months.  Pregnant mares can be taken to horse shows and trail ridden but there are several risk factors.  Stress can cause a drop in progesterone, a hormone which helps maintain pregnancy.  Also, if the mare becomes ill, she may end up losing the fetus either as a result of the infection or again the stress of being sick. 

Pregnant mares need vaccinations during their pregnancy.  At 5, 7 and 9 months of pregnancy, they need to be vaccinated for Rhinopneumonitis, the leading cause of abortion in pregnant mares.  Then four to six weeks before their due date, mares need to receive their annual vaccinations.  This time period correlates with high levels of antibodies to these diseases being available for the foal.  The most current thinking regarding when to vaccinate foals is at four to six months of age. The passive immunity that they receive from their mother needs to protect them during this time period.   Foals are born without any immunity; they only absorb these antibodies through the first milk or colostrum when they nurse within 12 hours of birth.  After that time period, these large proteins are no longer able to be absorbed.  A specific test has been developed to determine that the mare had good colostrum and the foal was able to absorb it.  This is the IgG test and a small amount of blood from the foal is tested.   We strongly recommend this test for any foal as it gives you confidence that the immune system will be able to fight effectively.  If the IgG test is low, the foal may need a plasma transfusion to gain the needed protection.  Although this is very effective, it is expensive.  It is much better to make sure that the mare has quality colostrum and that the foal nurses during the first 12 hours of life. 

There are several critical events which need to occur when the foal is born.  The mare needs to pass her placenta within 3 hours, the foal needs to get up and nurse within 2 hours and pass meconium within the first few hours also.  The mare should be bright and alert and she should also pass manure within 12 hours.  She should be interested in her foal and not painful once the placenta has passed.  More problems are seen in maiden mares, they are more likely to reject their foal and not let the foal nurse.  This is one reason why it is important to be around when your mare foals.

By taking good care of your mare during her pregnancy, you are setting the stage for a successful foaling.  Observe normal so that you know what abnormal is for your horse.  Call your veterinarian with any questions you may have and have fun with your foal.