Vitamins function as critical chemicals in the body’s metabolic machinery and function as cofactors in many metabolic processes. A deficiency of a vitamin will slow or block the metabolic process in which that vitamin is involved, resulting in deficiency symptoms. Vitamins are divided into those that are fat soluble -- that is, A, D, E and K -- and those that are water soluble -- B vitamins and C.
The bacteria in the rumen of the goat can synthesize adequate amounts of the water soluble vitamins. Thiamine, or vitamin B1, may become deficient under some conditions -- for example, feeding a high-concentrate diet, especially with high sulfur that may come from a high level of molasses. A thiamine deficiency can cause the disease polioencephalomalacia. Another situation that could lead to thiamine deficiency is improper feeding of the coccidiostat Corid®. The coccidiostat ties up thiamine, making the coccidia unable to reproduce. Feeding Corid® longer or at higher levels than recommended could lead to polioencephalomalacia. Polioencephalomalacia is a nervous disorder in which the animal becomes blind, depressed and presses with his head; and the pupil slit in the eyes becomes vertical rather than horizontal, which is the norm. Treatment requires immediate injection of large quantities of thiamine.
Fat-soluble vitamins must be supplied to the goat because the body cannot directly make them. The recommended level of vitamins in formulated feed is 5,000 international units (IU) -- a measure of the potency of vitamins -- of vitamin A per pound, 2,000 IU per-pound of vitamin D, and 20 IU per pound of Vitamin E. The liver can store significant amounts of the fat-soluble vitamins.
Vitamin A can be synthesized from carotene, the pigment that gives grass and hay their green color. As long as sufficient green feed is consumed, vitamin A intake will be adequate. Vitamin A is necessary for normal epithelium , or skin, development and vision. A deficiency of vitamin A causes many symptoms, including tearing of the eyes, diarrhea, susceptibility to respiratory infection and reproduction problems. Vitamin A is often supplied to animals not consuming green forage such as in winter months. Many mineral and vitamin supplements contain vitamin A.
Vitamin D is called the sunshine vitamin because animals can synthesize the vitamin with the help of the sun. Ultraviolet light in sunshine converts pre-vitamin D found in the skin to a pro-vitamin D form that is used by the animals. Usually, even limited sunlight exposure is adequate to provide a day’s supply of vitamin D. Sun-cured hay contains vitamin D. Vitamin D is necessary for calcium absorption and metabolism by the body. A deficiency of vitamin D, called rickets, results in lameness, weak bones and bowed and crooked legs. The liver is the main vitamin D storage site in the body. Vitamin D is normally present in mineral supplements and often added to complete feeds.
Vitamin E functions as an antioxidant in conjunction with the mineral selenium. The requirements for one can be partially met by the other. Thus, vitamin E is very important in areas with marginal or deficient levels of selenium. A common vitamin E deficiency disease, particularly in newborn or young animals, is white muscle disease, in which white spots are seen in the heart and skeletal muscle due to oxidation damage. A marginal deficiency of vitamin E can depress the immune system and cause reproductive failure. Green grass and green sun-cured hay have high levels of vitamin E. Most mineral supplements and complete feeds contain vitamin E, especially in areas that are deficient in selenium. Vitamin E is expensive and minimal supplemental levels are used in contrast to vitamins A and D that are less expensive and often included at generous levels.
Vitamin K is technically required by animals and functions in the clotting of blood. Vitamin K is produced by bacteria in the digestive tract and absorbed. Generally, goats do not need to be supplemented with vitamin K.
Reference: Hart, S. 2008. Meat Goat Nutrition. Pages 58-83 in Proc. 23rd Ann. Goat Field Day, Langston University, Langston, OK.