Vitamins are trace nutrients. They function as either cofactors or hormones. Vitamin E is an exception as it acts as an antioxidant. Vitamins are divided into fat and water-soluble groups. Fat stored vitamins have greater storage times, as they are soluble in lipids (fats).

Vitamin A
Found in many fruits and vegetables, it is missing in seeds. It has benefits to vision and the health of mucous membranes. Deficiencies can result in sinus infections as the tissue, weakened without it is less able to resist bacteria. It is stored in the liver.

Vitamin D3
Vitamin D3 is the form of vitamin D used by birds. It is synthesized from a compound in the skin when the skin is exposed to ultra violet light. If birds are exposed to unfiltered sunlight the do not need to be supplemented with vitamin D. The main effect of this vitamin is the mineralization of bone. Deficiency during growth results in rickets. In adult birds, soft-shelled eggs or thin-shelled eggs are formed. If there is long term deficiency in egg laying hens, bones demineralize and the result is osteomalacia.

Vitamin E
Vitamin E functions as an antioxidant, interacting with the mineral selenium to assist in the healing of oxidized tissues.

Vitamin K
The primary function of this vitamin is its role in the clotting of blood. It also appears to play a role in bone formation, deficiency resulting in skeletal deformities.

Water-soluble vitamins are required in the diet because they are cofactors for enzymatic reactions essential for normal metabolism. They cannot be made by the individual. They have short storage times and must be provided regularly.

Thiamin (B1)
Thiamin is found in grains so deficiencies are very rare. Polished rice is deficient in B1. Some fish have an enzyme that destroys B1 and should not be fed as an exclusive diet to fish eating birds. Deficiency results in neurological signs.

Riboflavin (B2)
Riboflavin is necessary for normal growth in chicks. A deficiency manifests as retarded growth, diarrhea and leg paralysis. It is also necessary for egg production. Chickens fed deficient amounts have reduced egg production. Seeds are deficient in B2.

Niacin
Niacin is formed from tryptophan. Corn and millet diets are deficient in this vitamin. Pellagra (black tongue) in chickens is the result of niacin deficiency.

Biotin
Biotin deficiency is associated with wheat and barley diets. Fatty liver and kidney disease is seen in chickens. Other signs of biotin deficiency are dermatitis of the feet, necrosis of toes, jaw deformities, and swollen eyelids.

Folic Acid
Folic acid is involved with carbon metabolism. It is a cofactor in the synthesis of purines. Uric acid, the white powder in a bird's droppings, is the main purine produced by birds and is the method by which nitrogen is excreted. Folic acid is found in many foods.

Vitamin B12
B12 is not found in adequate amounts in plants. It is known as the animal protein factor". It is stored for long periods of time in the liver. B12 should be supplemented in birds fed only plant diets.

Pantothenic Acid
Pantothenic Acid is a component of coenzyme A. It is found in seeds and is unlikely to be a dietary deficiency.

Pyridoxine (B6)
B6 is essential in a number of reactions related to nitrogen or amino acid metabolism. Deficiencies are unlikely on varied diets

Ascorbic Acid (C)
Most birds make C from glucose. Vitamin C is involved with the production of collagen and elastin in blood vessel walls. A deficiency will result in hemorrhage. Willow ptarmigan and bulbuls need to be supplemented. If in doubt Vitamin C can be supplemented as it is not toxic.

(Note) All the nutritional study in birds has been done on the domestic chicken which has great economic importance. Little is known about the needs of wild birds. Birds in the wild do not receive supplemental vitamins. They obtain their vitamins from their natural diet. It is difficult to feed each species kept in captivity its natural diet. For that reason if in doubt, I would recommend supplementing avacultural and pet birds with a good quality avian vitamin.

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