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Why Are Fat-Added Rations Becoming Popular for Feeding Horses?

David W. Freeman OSU Extension Equine Specialist

Horses do not have a gall bladder; hence, they do not store chemicals that assist the breakdown of dietary fat. However, the absence of a gall bladder doesn't necessarily mean that horses can't digest fat. In fact, a large amount of research conducted in the last quarter of the 20th century has shown just the opposite. Horses can readily digest upwards of 20% added fat in the total ration. However, palatability and the practicality of mixing fat in rations keep added-fat levels well below these high levels. Also, too high a level of fat (15 to 20% of the total ration) may decrease muscle glycogen stores because of too much replacement of dietary starch with fat. Muscle glycogen is the storage form of glucose, the energy component in starch. Glucose is the preferred energy source to fuel many types of athletic performance. Most typically, fat will be added to the grain portion of the ration. Fat supplemented grain mixes will contain less than 10% total fat as seen on feed tags.

Palatability tends to be higher for vegetable oils, and if a difference is noted, corn oil seems to be the most palatable among plant oils. Commonly used plant sources are corn and soybean oil, although many sources, including rice bran and refined dry fat, may be incorporated into horse rations with similar effects.

There are several advantages for adding fat and oil to horse diets. Energy supplied by fat replaces that needed from starch, thus lowering the incidence of starch overload colic and founder when horses are meal-fed large amounts of grain. As fat contains more energy per weight than carbohydrate or protein, less feed is required to meet the same digestible energy requirements. Digestibility of fat is higher than most other feedstuffs, so digestibility of the total ration is increased. Further, the digestible energy in fat-added rations is used more efficiently than conventional rations. If enough starch is fed with fat, and if horses are adapted correctly, fat supplementation will allow for more glycogen to be stored for intense athletic performance. Milk fat can be raised when lactating mares are fed fat added rations, resulting in increased growth performance of nursing foals. Apparently, addition of fat does not depress the digestibility of fiber, crude protein, and has little if any negative effect on calcium and phosphorus digestibility.

Adding fat will increase the cost of a ration. Even so, added-fat rations and fat supplements have become commonplace in the horse feed manufacturing industry. Fat added feeds are most popular in performance horse rations, broodmare rations and aged horse rations, all requiring highly digestible, safe sources of large levels of energy.