Optimum growth rates for various breeds have not been well defined, but overfeeding can cause developmental orthopedic diseases, and underfeeding can cause permanent stunting. Horses being exercised or worked require more nutrients, especially energy, than horses being maintained. Nutrients Horses need the same nutrients that humans do. In horses, as in humans, too much or too little can lead to serious health problems. Horses need a good supply of clean water daily.
Water is essential for all body functions, including temperature regulation and feed digestion.
The amount of water needed depends on the level of exercise, the ambient temperature, the quality of the feeds in the ration, and the proportion of the diet that is forage. This is the nutrient that primarily determines the weight and condition of the horse. Energy is derived primarily from carbohydrates, fats, and any protein excesses. Energy is needed for body functions, including maintenance, temperature regulation, digestion, work, etc. All energy that is provided above that which is needed will go toward the formation of fat.