Care must be taken when initiating a high-fat program. Avoid rancid fats and used animal fats as they are potentially toxic. The daily level should start at a few ounces and be increased gradually. The level should also be decreased gradually when the horse is removed from competition and high level training. If you feed almost any reasonable quality diet, sufficient amounts of digestible protein will be present.
Exercise seems to have little or no effect on protein requirement.
The little that is lost through sweat seems to be adequately met by the increased food consumption required by the increased exercise. Most of the necessary trace minerals will be in the pasture, hays and grains. The content may vary with soil concentrations, type of foodstuff and processing of that foodstuff. Therefore a free choice accessibility to a trace mineral salt block or lick may be advantageous. During heavy and prolonged exercise, excessive amounts of sodium, chloride, potassium, calcium and magnesium are lost through extensive sweating.