Dr. Stephen Duren, PhD

Fats and oils are commonly used in horse feeds to increase the calorie content of the feed or to replace the calories supplied by carbohydrates. Fat supplementation has many benefits including providing calories for weight gain, and providing essential fatty acids to improve skin and coat condition. Feeding fat has also been reported to decrease excitability in nervous horses.

Vegetable oils (corn oil, soybean oil, canola oil, rice bran oil) are all highly digestible; in fact, they are more than 90 percent digestible by horses. Horses will readily consume many different types of vegetable oil if given the opportunity to adapt slowly to the addition of fat in the diet. Horses will also consume sources of dry fat, such as high fat stabilized rice bran (20 percent fat) and spray dried vegetable oil. The fat contained in these sources is highly digestible, similar to vegetable oil, and the palatability is excellent.

Horses at work may require up to twice as much energy compared to horses at rest. Adding fat to the diet increases the energy density of the diet without decreasing performance, which means that horses in training do not need to eat as many pounds of grain to maintain their body weight. Photo: ©Dreamstime/Vanessa Van Rensburg

The initial goal in supplementing performance horse diets with fat was one of increasing the calorie content of the diet. Horses in training require an increased amount of calories the harder they work. In fact, horses in training may require twice as much energy compared to horses at rest. Traditionally, the increased energy requirement associated with exercise was satisfied by adding more grain to the diet. However, on an equal weight basis vegetable oil provides horses with two and a half times the digestible energy of corn and nearly three times the digestible energy of oats. Thus, adding fat to the diet increases the energy density (number of calories per pound of feed) of the diet. The net result of the high calorie content of a fat supplemented diet is that horses in training do not have to eat as many pounds of grain to maintain body weight. Reducing the amount of grain in the diet also decreases the chances of colic and grain overload founder. 

Horses that need to gain weight also benefit from the high calorie content contained in fat. Thin horses will gain weight and do so without having to eat as much grain if the diet is fortified with additional fat. 

Numerous studies have reported the potential benefits of fat supplementation to horses under a variety of exercise conditions. Although the jury is somewhat out on the clear metabolic advantages of fat, it is evident that feeding a fat supplemented diet will not decrease performance in horses that are adjusted to their diets. As a practical note, a high fat diet for a horse can provide 15 to 20 percent of the total calories from fat, while a high fat diet in humans can provide 60 to 70 percent of the total calories. Therefore, even horses receiving a significant amount of vegetable oil do not suffer any potential health consequences as seen in humans consuming too much fat.

During the summer months, ambient temperatures rise, and horses have the extra physiological burden of keeping themselves cool. Two nutritional considerations should be made for feeding horses during summer. First try to minimize the amount of body heat produced by the diet. Research has shown it is beneficial to provide some of the calories required by horses as dietary fat. Since fat contains more than twice as many calories as cereal grains, a horse eating a fat supplemented diet will need to eat fewer pounds of feed. This lower feed intake results in less body heat produced during the digestive process.

The lower glycemic response with fat supplemented diets has led to promising results for horses that suffer certain types of tying-up syndrome. Photo: ©Dreamstime/CustomPosterDesigns

Research concentrating on the glycemic response of grain meals fed to performance horses found that sugar response of a grain meal was drastically reduced if the meal contained fat. This lower glycemic response with fat supplemented diets has led to promising results for horses that suffer certain types of tying-up syndrome. The mechanism by which the addition of fat alters glycemic response has been reported to be a general slowing of the rate of stomach emptying. The fact that dietary fat does not contain sugar, and that adding fat to the diet results in general decrease in glycemic response, also may be helpful in controlling behaviour in horses that become hyper when fed large amounts of grain. This is not to say that feeding fat will calm the savage beast, but it may modify behaviour enough to be noticeable.

It should be apparent that dietary fat in the form of vegetable oil, high fat stabilized rice bran, or spray dried vegetable oil is beneficial for performance horses and for horses that need to gain weight. Fat is both palatable and highly digestible by horses. Further, feeding fat does not result in digestive upset that may occur when large amounts of grain are added to the diet. 

This article was originally published in the June 2015 issue of Canadian Horse Journal.

Main Photo: ©Dreamstime/Chelle129