Question
A nine-year-old pregnant mare just arrived at a body condition score of 3. She is due to foal in about two months. She’s consuming 6 lb (2.7 kg) of sweet feed and free-choice hay, which is a grass-alfalfa blend. My vet is worried that she has too much fiber in her diet, and I am concerned that I will not be able to get her to a healthier weight before foaling, as it’s been my experience that most mares in late pregnancy have decreased appetites. Any suggestions would be welcome.
Answer
Because her gastrointestinal tract is engineered to process forage—and lots of it—I would not be concerned with offering your mare too much fiber. As you allude to in your question, though, supplying sufficient calories for weight gain and fetal growth can be challenging.
The sweet feed you mention in your question is not the best choice for your mare because it has little added fat and, more importantly, is low in vitamin and mineral fortification. A few changes to the diet would provide your mare with not only more calories to support her and her foal but also a complete vitamin and mineral profile.
To provide optimal levels of lysine, minerals, and vitamins for fetal development, I recommend switching to a high-calorie feed formulated specifically for breeding and growing horses. These feeds often use a variety of ingredients to meet caloric needs, including fermentable fiber (soybean hulls, beet pulp), cereal grains (oats, corn, barley), and fat (rice bran, oil). Feeds with added fat (6% or more) will generally provide the energy density necessary for late-pregnant and early-lactating mares.
Late gestation is a time of mounting energy needs for mares, so it’s imperative that she is fed sufficient quantities of feed. Carefully review the feeding instructions of the new feed to make sure she’s consuming at least the minimum amount recommended. Considering her energy needs, she will likely require significantly more than the minimum. No single grain meal should exceed 5 lb (2.8 kg), and feeding the total amount in three or four meals a day might prove beneficial.
In addition to a more suitable feed, fat supplements such as vegetable oil or stabilized rice bran can be top-dressed onto the feed to boost energy intake.
Any feed changes, whether you decide to switch to a more appropriate feed or add a fat supplement, should be done gradually over the course of 7-14 days, starting with a small amount and building up slowly to allow the digestive system time to adapt.
The hay you describe seems appropriate for a pregnant mare, and it’s best to give her 24/7 access to the hay, as you’re doing. In considering the forage component of the mare’s diet, the only thing you might do to increase its caloric contribution is to switch to a high-quality alfalfa hay. In some regions, alfalfa is difficult to obtain or expensive, so as long as the hay you’re feeding is palatable and plentiful, the forage is acceptable.
Supplementation with vitamin E is also beneficial for underweight horses to rebuild their levels and support immunity and foal health. Nano•E offers superior bioavailability, according to research conducted at Kentucky Equine Research.
