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.

Conscientious owners should be aware that there can be potentially toxic substances in feeds.

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.