Vitamins play a number of key roles in the diet of the horse. Vitamins are organic, meaning that they consist of complexes of living enzymes. They are needed for healthy body tissue and energy. They are also important in supporting the immune system and wound healing.
There are two types of vitamins: Fat Soluble and Water Soluble.
Vitamins A, D, E and K are fat soluble. They dissolve in fat and any excess will be stored in the body fat and liver. It is important to monitor the levels of fat soluble vitamins being provided as excess levels can cause serious health problems.
Vitamin C and the B vitamins are water soluble. They dissolve in water and any excess is excreted in the urine.
Fat Soluble Vitamins — A, D, E and K.
Vitamin A is a fat soluble, antioxidant vitamin. It is important for proper eye function, healthy skin and hooves. It is also needed to maintain healthy epithelial tissue in the respiratory, digestive and reproductive tracts. It also regulates bone development in young growing horses. Vitamin A deficiency can cause night blindness, shedding, progressive weakness, dry hair coat, diarrhea, decreased growth, impaired mineral delivery, decreased intestinal absorption and susceptibility to infections of the respiratory and reproductive tracts.
Vitamin D is a fat soluble vitamin. Its main role in the body is calcium homeostasis, or keeping the calcium levels at a constant level. Vitamin D is also critical to proper growth. A Vitamin D deficiency can cause a reduced growth rate, bone weakness, increases in bone demineralization, lameness and loss of appetite. It can also cause a depletion of calcium. If a horse is exposed to plenty of sunlight then a Vitamin D deficiency is unlikely.
Vitamin E is a fat soluble antioxidant. It is essential for growth, proper muscle development and function, oxygen transport and red blood cell stability. It is also believed to be important for the proper function of the immune system. Vitamin E also acts as a vasodilator which opens up blood vessels so that blood flows more freely through tissues. It can also help reduce toxic oxide compounds in the tissues during periods of intense exercise. Vitamin E deficiency in horses causes swelling of the joints, loss of coordination, poor wound healing, rickets and nutritional muscular dystrophy or White muscle disease which is a degenerative disease that affects the heart and skeletal muscles of foals under a year of age.
Vitamin K is very important for blood clotting. It helps to produce what are called the Gla-proteins which are intricately involved in the complex process of blood clotting. Vitamin K is also important in bone metabolism and heart health. Vitamin K deficiency is rare as there is plenty of it in forage and cereal grains. One note of caution is that it has been shown to be affected by moldy hay—particularly sweet clover hay. This can work as an agent to prevent Vitamin K from doing its job.
Water Soluble Vitamins — B and C.
Vitamin B1 or Thiamine is an essential part of several enzyme systems. It is involved in the release of energy from absorbed or stored carbohydrates and fats. It also seems to have a direct role in the activity of the nervous system, stimulating peripheral nerves. When fed in higher quantities, it can also calm nervous horses. Vitamin B2 or Riboflavin is a precursor to two coenzymes. Flavin Adenine Dinucleotide (FAD) and Flavin Mononucleotide (FMN). Coenzymes are molecules that carry chemical compounds between two enzymes—very important to transport many substances in the body. Being a precursor simply means that the equine body uses B2 to make the coenzymes.
Vitamin B3 or Niacin is one of those vitamins that is essential to almost everything your horse does. It is involved in the metabolism of fats, carbohydrates, and amino acids. It also functions as a vasodilator and helps to increase blood flow to the extremities.
Vitamin B5 or Pantothenic Acid is found numerous places in the body. It is important in converting proteins, carbohydrates, and fats into energy.
Vitamin B6 or Pyridoxine is a part of most of the enzymes that aid in the metabolism of fats, carbohydrates, and proteins. As such, it is a very important for energy production, nervous system activity and for blood production.
Vitamin B7 or Biotin is found in virtually every cell in the body and is an essential coenzyme in carbohydrate, fat, and protein metabolism. It is also important for thyroid and adrenal gland function, reproductive tract health, stability of the nervous system and most importantly to maintain healthy coat and hooves.
Vitamin B9 or Folic Acid has many functions in the body but, perhaps, the two most important functions are its role in the formation of red blood cells and its involvement in DNA synthesis.
Vitamin B12 or Cyanocobalamin is an essential part of several enzyme systems. It is involved in carbohydrate and fat metabolism, as well as protein synthesis. It is particularly important in helping to maintain the manufacture of red blood cells.
Vitamin C or Ascorbic Acid is primarily an anti-oxidant and is important for combating free radicals and helping the immune system fight off infections. It is also vital to the formation of healthy connective tissues.
Deficiencies of antioxidants would include poor wound healing, reduced performance and frequent infections.