by Randy L. Stanko, Ph.D., Texas A&M University-Kingsville
Vitamin A is predominantly stored in the liver but can also be found in fat and other organs. Cattle need vitamin A to maintain proper kidney function and epithelial tissues like skin and the linings of digestive, respiratory, and reproductive tracts. Vitamin A is also necessary for proper development of bones, teeth, and the nervous system, and is important for vision when an animal adjusts from light to dark. In fact, a sure sign of vitamin A deficiency is night blindness. Other deficiency signs include loss of appetite, rough hair coat, dull eyes, and reduced gain and feed efficiency. Low fertility, abortion, dead or weak calves at parturition are also signs of vitamin A deficiency in the cow herd. Vitamin A can be included in dry or liquid protein supplements, and in mixed feeds or given as an intramuscular injection. Unless consuming green forage or green legume hay, young, growing cattle need 15,000 to 20,000 IU of vitamin A per day while similar fed bred cows and lactating cows need 30,000 and 45,000 IU of vitamin A per day, respectively.
Vitamins D is critical for proper bone growth and maintenance, calcium absorption, phosphorus absorption from the kidney, and immune function. Vitamin D deficiency can cause rickets, swollen and stiff joints, anorexia, muscle tetany and convulsions but is rarely a problem because as long as cattle are exposed to sunlight their skin has the ability to synthesize vitamin D. Problems can occur if cattle are housed indoors for long periods of time and fed a high-concentrate ration (little or no hay). Vitamin E is necessary for muscle growth and structure and serves as an antioxidant that prevents cell damage, as well as many other cellular and metabolic functions. Symptoms of vitamin E deficiency include heart failure, paralysis, and general muscle dysfunction, including the tongue which impairs suckling. Sun cured-hay and certain fish liver oils contain high amounts of vitamin D while vitamin E occurs naturally in green feedstuffs and seeds/oilseed; however, amounts of vitamin E in forage crops generally decreases as plants approach maturity or are harvested. Requirements for vitamin E in growing cattle range from 7 to 27 IU/lb of gain and in older cattle, 50 to 100 IU/day. Animal health companies provide injectable vitamin A, D, & E, either separately or in combination at very comparable prices [cost per cow = $1 to $1.50]. Cheap Insurance!