Home > Crops & Livestock > Livestock > Horses > Nutrition > Digestive System A horse has an unusual digestive system and its needs differ because of its athleticism. Proper Nutrition [Image: Grazing Horses] The horse production areas of primary importance are growth, reproduction, lactation and work. Nutrient Requirements The daily nutrient requirements of the horse are based on a critical need for protein, energy, vitamins, minerals and water, to enable the horse to do a specific job and achieve his genetic and physical capabilities. Minerals For Horses The primary concern in mineral nutrition is to provide salt and adequate levels of calcium and phosphorous in approximately a 1.3 to 1 ratio.  more articles... Vitamins For Horses Vitamin supplementation in horses is generally not needed since common feeds normally contain adequate amounts. Vitamin deficiencies occur primarily when horses are sick or stressed, or if feed is improperly processed and stored over long periods of time. In these cases, vitamin supplementation may be necessary. Toxicants in Feeds, Hay and Forages [Image: Baling alfalfa hay] Conscientious owners should be aware that there can be potentially toxic substances in feeds. Somatotropin Benefits Doubtful for Growing Horses Somatotropin, also known as growth hormone, is a protein hormone produced and secreted by the pituitary gland of mammals. Somatotropin has several functions in the body, the most notable of which is growth of the long bones (for example, the femur of the thigh), which is achieved via stimulation of an intermediate hormone, insulin-like growth factor-I (IGF-I), from the liver.