Vitamins are an important nutritional component in cattle diets. Vitamins are a specific class of nutrients that are required for efficient metabolic processes and enable cattle to utilize other nutrients. For cattle, it is only essential to supply the fat-soluble vitamins A, D, and E because rumen bacteria can synthesize vitamin K and the B vitamins to meet animal requirements. The fat-soluble vitamins can be stored in the body, and in the case of older cattle, it can take 100 to 150 days to deplete these stores. Consequently, not replenishing lost body stores of vitamin A could result in production and economic ramifications up to 6 months later.
Vitamin A needs special attention in beef cattle rations as it is important in many metabolic functions. Night blindness is the classic symptom of Vitamin A deficiency. One of its functions is the maintenance of epithelial tissue, such as the skin and lining of the respiratory, digestive and reproductive tracts to keep them in healthy condition. It also plays a role in eye health, proper kidney function and normal development of bones, teeth and nerve tissue. Other signs of vitamin A deficiency in growing cattle include low intakes, rough hair coat, lethargic movements, reduced daily gain and feed efficiency. Most of these symptoms are common in other diseases or deficiencies and may not be easily recognized as a vitamin deficiency.
Green leafy and yellow plants contain carotene, a pigment which animals convert to vitamin A. In the spring and early summer months when plants contain high amounts of carotene, Vitamin A deficiency is not usually an issue. However, during the rest of the year when cattle are consuming mature, stored forages or processed feeds, the chances of vitamin deficiency increase. Fall and winter seasons are when the body stores might become depleted and deficiency symptoms may develop.
In the breeding herd, Vitamin A is important for maintenance of pregnancy in the cow and spermatogenesis in the bull. At parturition, colostrum is the source of vitamin A for a newborn calf which demonstrates the need for proper supplementation of cows prior to calving.
Vitamin D is formed by the action of sunlight or other sources of ultraviolet light rays upon certain sterols. If cattle have exposure to sunlight, or harvested hay, deficiency is seldom an issue. Young, growing animals have a greater requirement for vitamin D than mature animals. The requirement for young, weaned or starting calves is approximately 300 IU of vitamin D per 100 pounds of body weight. While it is easy to meet the cattle requirements of Vitamin D, that does not reduce its importance in the absorption of calcium and phosphorus. Vitamin D helps regulate blood calcium levels and the conversion of inorganic to organic phosphorus. It also aids in the formation of sound bones and teeth.
The primary functions of Vitamin E are to form structural components of membranes and inhibit oxidation of other molecules. There is a close relationship between selenium and vitamin E as both nutrients work in conjunction with the other. White-muscle disease in calves has been prevented and cured by the use of vitamin E and selenium supplementation. Vitamin E is important for muscle and vascular function as well as supporting the immune system and disease prevention. Green forages and whole grains are sources of vitamin E.
Ted Perry -Beef Technical Solutions