Energy Sources for Racehorses

When horses exercise, their bodies must release energy stores into the blood to fuel muscles. Complex chemical pathways release enough energy to meet the demands of work as quickly as possible. Energy is commonly supplied by carbohydrates in the form of starch and sugar derived from cereal grains, but the use of alternative energy sources for performance horses is now common across the world.

Energy is stored in the horse in two major forms, glycogen and fatty acids. Glycogen is a sugar that can be released quickly for immediate use, such as when a horse accelerates to full speed from a standstill. Fatty acids are stored in adipose or fat tissue and are released more slowly as a horse achieves its stride and works mainly in the aerobic zone.

The difference in size of these two energy stores is quite immense: the average 500-kg racehorse stores around 75MJ of energy as glycogen compared to a massive 640MJ as fat. The metabolism, or “burning,” of fat requires glycogen, so if glycogen runs short the horse is no longer able to use fat for energy.

Once glycogen stores are depleted, the horse will fatigue. Many trainers are familiar with horses suddenly slowing down after the first half of the race. Because the body can no longer keep up with the energy demands of the muscles, the horse quickly slows its pace. This sudden energy depletion and resulting fatigue can mean the difference between running to a strong finish and suddenly falling to the back of the pack.

During aerobic work of medium to long duration, such as racing, the horse should be predominantly utilizing its stores of fat to power the athletic effort, rather than using up the limited on-board stores of glycogen. This is where alternative energy sources can help, and the most common of those is fat.

With an appropriate adaptation period, horses can switch which energy source they use preferentially during exercise. That is, horses can begin using fat rather than glycogen as the major energy source for muscles. During training and conditioning, horses naturally start to use more fat for energy as they get fitter, but the effect can be maximized by feeding additional fat.

A diet is described as high in fat when a significant proportion of the total calories are provided in the form of fat, usually either vegetable oil or other high-fat supplements such as a stabilized rice bran (such as Equi-Jewel). A ration including 1-2 cups of vegetable oil or 500g to 1kg per day of Equi-Jewel would be described as a high-fat diet.

Horses fed a diet high in fat begin to burn more fat and use less glycogen during work efforts. The metabolic switchover previously mentioned takes about one month of feeding and working the horse continuously, so just adding fat in the days before the race will not give the desired result.

What type of fat is best? There are no definitive answers as to which fat might maximize the glycogen-sparing effect. Canola oil appears to be one of the better vegetable oils, having reasonable omega balance and being readily accepted by most horses. Other vegetable oils such as sunflower or soy oil are also fairly good. Corn oil may not be the best option as research has suggested that corn oil has a poor omega balance. This poor balance can actually raise working heart rates and blood lactate levels, but corn oil is very palatable and may be useful for fussy eaters.

Equi-Jewel stabilized rice bran is research-proven to reduce working heart rates and lactates, when compared to oil. The other advantage of Equi-Jewel is that it is a palatable dry pellet that is readily accepted by horses adverse to oily feeds. Equi-Jewel also contains natural vitamin E and organic selenium to assist with rapid muscle recovery in hard-working horses.

Other high-fat supplements include sunflower seeds and soya bean meal. With these supplements, consideration must be given to their high protein content, as they may provide excessive protein in the diet if used as a fat supplement.

Remember, fat contributes a significant number of calories to the diet, so a reduction in grain may be necessary to avoid a horse becoming too fat. A rule of thumb: 1 cup of oil or 500g or high-fat stabilised rice bran supplement is equivalent in calories to about 1 kg of whole oats, and slightly less of steam-flaked corn or barley.

You will need to feed as least 1 cup per day of oil or 500g per day of a high-fat supplement. Continue daily with high-fat feeds for at least four weeks to get the full benefit of glycogen-sparing.

If you want to maximize your horse’s energy metabolism and want to prevent fatigue during a race, add fat to your horse’s diet. As a bonus you’ll get a nice shiny coat, and maybe even some wins as your horse powers home with energy to spare.