Q.My hard-keeping Thoroughbred does low-level eventing and is a picky eater, especially when he’s not working. Even though he has free-choice hay access, he only eats three to four flakes a day. Pasture in the summer helps, but now the pasture is gone for winter. He also won’t eat supplements … he sifts through or won’t eat any of his grain. How can I get calories into him?

—Lynn, Versailles, Kentucky

A.To start answering this question, it’s necessary to first visit why your horse is a picky eater. Some horses are simply picky eaters and hard-keepers, just like some people are! But others might have a reason that they don’t want to eat, and unlike people who have similar reasons, they can’t speak up and explain that to us.

Rule Out Health Problems

If a horse doesn’t have a good appetite, first and foremost a veterinarian should assess him for causes of a poor appetite. A proper oral examination might indicate your horse is overdue for a dental float, or he might have a tooth that’s causing him pain. Blood work could evaluate his organ function (especially that of his kidneys and liver) and rule out the possibility of an underlying infection. Examination by a veterinarian might also aid in determining whether your horse has gastric ulcers (via a gastroscopy) and requires empiric anti-ulcer therapy.

Trial and Error

Assuming your veterinarian has ruled out pathologic reasons for a poor appetite, then it’s possible your horse is simply a picky eater, and the goal becomes increasing his caloric intake. Consider offering different types of forage or grain to find something he finds palatable. Alternatively, consider adjusting his environment to determine if social hierarchy might be affecting his appetite (i.e., more aggressive horses are preventing him from eating).

Calculate the Calorie Deficit

If none of these strategies is successful, go back to basics and figure out how much the horse is actually eating.  This is necessary because it dictates how to proceed with adjusting his diet. A 1,000-pound horse who’s not in work needs approximately 15,000 calories per day to maintain his body weight. The daily caloric requirements of the same horse can increase to well over 20,000 calories per day when he’s in work. Different breeds of horses have different metabolic rates, so these numbers can vary quite a bit for individuals. However, it’s helpful to determine these needs and work backward from them.

A pound of good-quality timothy hay contains about 800-1,000 calories. A pound of a complete pelleted feed contains about 1,000-1,200 calories. A horse should get most of his calories from these two types of feed, in addition to good-quality grass when possible and indicated. A pound of sweet feed contains about 1,500-1,700 calories. Sweet feed can be a helpful component of a horse’s diet, but it shouldn’t be a primary source of calories, because it ferments rapidly and can increase colonic gas production.

Once a horse’s average daily intake is determined, you can calculate his calorie deficit. If a deficit exists, you can make up the difference by incorporating a high-fat supplement into his diet. Several nutritional companies produce high-quality fat supplements that complement a horse’s diet well. These products often contain high-fat feeds such as rice bran and flaxseed, as well as vegetable oils. A pound of a high-fat supplement contains about 1,900-2,100 calories. It’s also possible to add rice bran or corn oil to feeds on their own, but many owners prefer products from a nutritional company, because these supplements are already neatly packaged, carefully formulated, and don’t require the extra mess or work. Introduce any high-fat supplement to a horse’s diet slowly and gradually, because a dramatic change in nutritional content can set the horse up for gastrointestinal upset and even diarrhea.

With these strategies, you can approach a horse’s finicky attitude toward feed more effectively. The feed recommendations I’ve provided are general, because hay quality can vary considerably and the composition of similar feeds offered by different companies can also differ significantly. Moreover, different breeds of horses have important nutritional considerations. Horses are much more reliant on the health of their gastrointestinal microbes than humans, so sudden changes to the diet can have serious consequences. I recommend consulting your veterinarian or equine nutritionist before making changes to your horse’s diet.