Continuing our discussion on preparing the mare to foal, today we will discuss neonatal isoerythrolysis.  Dr. Thomas Riddle from Kentucky indicates this disease is seen in 1% to 2% of the equine population.  The disease occurs in a foal when it ingests colostrum that contains antibodies which react with the red blood cell antigens the foal received from the stud, and the foal’s red blood cells are destroyed.  To prevent this problem, mares can be tested 2 weeks before foaling for antibodies.  If a mare tests positive, the foal must not be allowed to nurse the mare for 24 to 36 hours and the foal must be fed with donor colostrum.  Horses also have different blood groups just like people and the most common groups to react are CA, AA, and UA. 

Next we will look at general nutrition in the late term mare.  Dr. Riddle indicates that in Kentucky, excessive nutrition is far more common than inadequate nutrition; this is also true in our practice in Texas.  Excessive nutrition during pregnancy combined with stress has been suggested as a cause of reproductive problems, including placental disease.  The mare should receive 2 ¼ to 2 ½ percent of her total body weight in feed.  During pregnancy, the average thoroughbred mare gains around 200 pounds and most of this is in the last 3 months.  The total diet should contain 12% to 14% crude protein.  To determine your mare’s crude protein level in the diet, the hay, concentrates, and pasture must be evaluated.  A total ration analysis will also reveal the amount of calcium and phosphorus so you can determine if the calcium phosphorus ratio is correct at 1.2-1.5 to 1.  It has been theorized that diets too high in calcium, such as those relying on large amounts of alfalfa, could be related to the development of joint lesions in the foal.  It is essential that the mare ingest adequate quantities of minerals for normal fetal growth.