Q: How can I balance calorie density and fiber content in my horse’s feed to optimize his performance without sacrificing gut health?

A: Performance horse nutrition focuses on providing energy for work and ensuring a balanced intake of protein, vitamins, and minerals to support both activity and recovery, while also promoting good gut health. These horses require more nutrients compared to less active horses, but the exact amount depends on how often, how long, and how intensely they work. If your horse’s forage is of high quality and their workload is lighter, forage, hay, or pasture is more likely to cover most of their nutritional needs.

With increased performance level comes higher energy demand. Energy, measured in calories, provides fuel to run the system and do physical work. Body condition is a good indicator of whether dietary calories are meeting the demand. While there might be some individual variation, performance horses are at their best when maintained in a moderate body condition score of 5–6, where you can easily feel but not see the ribs.

Energy Sources for Performance Horses

While it is easy to determine when total energy needs are being met, understanding the sources of energy used during exercise is a bit more complicated. A horse’s primary energy stores are body fat deposits and glycogen (a complex sugar) stored in the liver and muscles. Body fat is the major energy source for low-intensity aerobic activities performed over several minutes or even hours. It is supplied primarily by dietary fats and fibers. Glycogen is the main fuel source for higher-intensity anaerobic work that lasts for seconds or a few minutes. The horse gets this from dietary starch and sugar. Protein is not a major or efficient energy source. When horses run low on glycogen, though, they start relying on protein for energy. Ideally, protein maintains muscle mass and is a component of antibodies, enzymes, and some hormones, include insulin, growth hormone, and parathyroid hormone, which play vital roles in regulating various physiological processes in the body.

The level of stored energy in these body “fuel tanks” depends on the amounts and sources of calories available from the diet. Horses eat plants, which store energy as carbohydrates and a small percentage of fats. Dietary carbohydrates are composed of starch, sugar, and fiber. Hay and pasture provide more calories from fiber, though some pasture grass and hay can have relatively high sugar content. Grains such as oats, corn, and barley provide more calories from starch. The body converts calories from fiber primarily to volatile fatty acids, which provide the majority of energy for the horse at maintenance but have limited capacity to fuel hard work. The horse’s body absorbs starch and sugar calories as glucose, which is available immediately for work or stored as glycogen. Once the glycogen fuel tanks are full, additional starch and sugar calories contribute to body fat stores.

Choosing the Right Feed for Performance Horses

The reason for feeding grain has traditionally been to supply calories when hay or pasture alone wouldn’t maintain body condition in working horses. Oats and corn provide significantly more calories per pound (1,200–1,500 kilocalories/pound, respectively) than good-quality hay (800–1,100 kcal/lb). Higher-calorie, more digestible fiber types such as soy hulls, beet pulp (both average 1,000 kcal/lb) and wheat middlings (1,500 kcal/lb) have replaced some or all of the grain in modern performance feeds.

Fats provide a high concentration of calories and are an efficient energy source, by including fats in formulas, you can decrease the amount of feed needed to meet a horse’s caloric requirements. Fat provides 2.25 times the caloric content by weight compared to starch and sugar, while also producing less heat during digestion than carbohydrates, particularly fiber. In practical terms, one pound of fat (equivalent to two cups of vegetable oil) supplies as many calories as three pounds of oats or approximately four to five pounds of hay.  

Formulating feeds with higher fats and digestible fibers has allowed feed manufacturers to replace some or all the grains while maintaining high calorie density. This helps more safely meet high calorie demands of performance horses in a lower volume of feed. A reliable rule of thumb that helps optimize gut health is to keep supplemental feed meal sizes at a maximum of 0.5 pounds of feed per 100 pounds of body weight (5-pound feed meals for 1,000-pound horses).

Take-Home Message

The ideal mix of fuel sources depends on a horse’s performance needs. Fats mainly power aerobic work, while glycogen fuels anaerobic activity; dietary fats and fiber do not rapidly restore glycogen. Providing good-quality hay and a well-formulated feed with balanced nutrients and appropriate calorie sources supports both performance and gut health.

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