Nutritional demands by the horse's body increase and change as the exercise level increases. As the conditioning program changes, the energy demand is met by increasing the food intake and/or changing the grain:hay ratio.

The increase in energy requirements due to exercise depend on the duration and intensity of the exercise, the weight and ability of the rider or driver, the type of footing and/or terrain and the weather.

If a horse is losing weight because of the increased need for energy to meet the workload, it means the energy content is too low at the current level. Most horses have an optimal body weight at which they perform best, and it is important for this weight to be maintained by increasing energy content of the feed.

During exercise, water is lost in sweat, and unless the loss is replaced promptly, dehydration that limits performance develops. Fluid losses in horses competing in endurance rides often reach as much as 10 percent of body weight.

Energy = performance

According to a study done by Cymbaluk in 1988, the energy expended during different types of exercise and the amount of oats necessary to support energy demands is as follows:

As a horse progresses through a conditioning program or through a series of competitions, the higher workload is usually supported with an increase in carbohydrates, usually grains, while reducing the amount of hay. Grains supply more calories in a smaller volume which is conducive to both better performance and better appearance.

In some cases, fat is added to the diet because it is energy dense and low volume. Fat supplies more than twice the calories of carbohydrates on a weight basis and this is particularly beneficial in fit horses that limit their voluntary food intake.

Fats are used as energy by aerobic metabolism especially during prolonged endurance exercises. Horses that are aerobically fit use fats to a greater extent than horses that are not so fit. Fat helps preserve glycogen stores and allows the horse to maintain a higher blood glucose level during prolonged exercise.

Generally, the requirement for protein increases very little with exercise and any additional need is easily met by the overall increase in the feed ration. Usually no protein supplement is needed and too much protein in the horse's diet may impair performance because of increased fluid losses and the precipitation of fatigue especially in endurance horses.

Any increased need for vitamins and minerals is usually met by the increase in feed necessary to meet the energy demands of the horse, although horses that are stabled much of the time may require some supplementation on an individualized basis.

Of course, plenty of fresh, clean, palatable water should be accessible to horses at all times. Without adequate water, the horse's body cannot make the best use of the nutrients in the feed. In addition, exercise increases the amount of water and electrolytes lost in sweat. It is important for horses to be fully hydrated at the start of any exercise program or competition.

On the day of a competition, the feeding regime can have an enormous effect on performance. Most research indicates that a meal of hay and grain fed about 4 hours prior to the beginning of competition allows time for stabilization of the glucose and insulin levels in the horses body.

For horses competing in endurance events, a meal of 4 to 7 pounds of hay and about 4 1/2 pounds of grain with electrolytes can be fed about 4 hours before the beginning of competition. This combination of feed maximizes fluid retention, and the fibrous content of the hay stimulates the horse to drink, while the electrolytes help hold the water in the intestine to make up for fluids lost in sweat.