Horses fed high-fat diets appear to perform better than those fed either a high-starch diet (40%) or a high-protein diet (25%) for both high-speed (racing) activities, and moderate-speed activities (fast trot/slow canter speeds of about five meters a second). Resaerch showed that their blood glucose levels decreased less, and for a shorter duration, than did those horses on high-carb diets. These benefits might produce only subtle results—but even a gain of a few feet on a racetrack might result in a Derby win. Even at lower levels of performance, the change can be valuable. For example, a low-goal polo player might find that his horse can recover more quickly and, perhaps, be able to play one more chukker than before. But, that’s not to say that fat is a miracle ingredient. For reasons we don’t yet fully understand, the horse’s body must “learn” to use fat as an energy source, a process requiring considerable metabolic adaptation on the part of the muscle cells. It can take three to four weeks, and the blood chemistry might continue to adapt for up to six weeks. What this means is that you can’t just start feeding fat the day of the big race and see results. Not only do you have to put your horse on the fat-supplemented diet a good month in advance, but you also have to challenge his system so that it begins to adapt. For a racehorse, that means you have to race him on the new diet, not just train him conservatively, to help him begin to assimilate the new energy source. And as nice as it might be to contemplate improving further on the benefits of feeding fat by feeding greater amounts—perhaps eliminating grain altogether—unfortunately, it just doesn’t work that way. Remember that only carbohydrates can fuel the anaerobic system of metabolism, which all horses use to some degree in their work—and that forages alone provide a minimum of carbohydrate. (Fed by itself, forages provide plenty of fuel for maintenance metabolism but not enough for many horses to do the work we ask.) Grain in the diet is an important fuel source for any performance horse, and study after study has confirmed that high-fat diets work best in conjunction with fairly high-grain diets, for maximum benefit in hard-working horses (such as 100-mile endurance racers, Thoroughbred and Standardbred racehorses, and upper-level three-day-event horses). The exception is horses with a genetic defect called equine polysaccharide storage myopathy, which have difficulty using carbohydrates as an energy substrate; a prescribed diet in which fats almost completely replace grains usually allows these horses to continue to perform. So what level of fat is optimum for a performance benefit? That number is still under debate. Some researchers now recommend a level of 10% (by weight) of the total daily diet for horses working at the extreme end of the athletic spectrum, though slightly lower levels (about 8%) might be more appropriate for horses working at a lower level of intensity. The level of fat you choose might depend somewhat on the activity you’re asking your horse to perform. Some studies have indicated that levels up to 15% are beneficial for horses involved in intense, long-term endurance activities (chiefly competitive trail and endurance racing, and upper-level three-day eventing). However, even a level of 6% to 8% will result in some performance benefit for horses involved in more moderate activity. Feeding fat can also be well worth considering for reasons other than performance enhancement—good news for the vast majority of us, who are dealing with horses not at the cutting-edge of high performance. First, it’s true that supplemental levels of fat can enhance the quality and shine of the hair coat, giving your horse a healthy glow that reflects particularly well in the show ring. Supplemental fat also can help put or keep weight on a “hard keeper.” Just as we do (far too efficiently, sometimes!), horses will store excess fat in the adipose tissues—so for plumping up a skinny horse, added fat is an excellent solution that carries far less risk of stomach upset and other complications than does a switch to a high-carbohydrate diet. As the condition of their teeth starts to deteriorate and their digestive efficiency wanes, older horses might benefit from a high-fat diet, too. Easily digested fat can help prevent them from losing condition and becoming ribby. By the same token, broodmares can reap the rewards of added fat. Studies have indicated that a mare that has recently “gained some condition” (easily achieved by feeding added fat for a month or two before breeding) might catch more easily and maintain her pregnancy with less difficulty. In addition, a high-fat diet can help her deal with the stress of lactation, which can be considerable. A third perk is that her milk will be higher in fat (mare’s milk being fairly low to begin with), and as a result her foal will tend to gain weight and condition more easily. article first published by Karen Biggs
