Plants do not contain vitamin A in active form, but in the form of precursors thereof as carotenoids (yellow pigments found associated with the chlorophyll and responsible highly colored red and yellow legume): alpha, beta and gamma. In birds the beta-carotene is the most active of all.

The carotenes are considered pro-vitamins. Animals can not synthesize, but it may take to form. active (vitamin A) in the intestine and liver. Approximately 90% of vitamin A in the body is stored in the liver. These reserves can be exploited in any state of emergency, when through the diet does not bring enough.

Excessive carotene in the diet causes an orange-yellow skin, but never give rise to vitamin A toxicity (hypervitaminosis) because the agency never transform these precursors to active form unless you need it.

Sources:

The carotene found in yellow and green leafy vegetables: cabbage, turnip greens, carrots, spinach, lettuce, beets, squash, dandelion, and in fruits such as apricots, peaches, melons, etc.. The more intense the green or yellow fruit or vegetable contains more carotene concentration.

The cod liver oil and halibut are important sources of vitamin A in an active way.

Functions:

Helps preserve in normal epithelia. Its deficit causes a disturbance (keratinization) of the skin and mucous membranes lining the respiratory tract, urinary tract, genital tract and ocular epithelium. This represents a decrease of forming a protective barrier membranes to protect the body against infections: pathogens can easily penetrate and cause infection.

Its lack produces:

- Alteration of the mucous membranes: oral cavity with sterile abscesses inflamed or infected. Small white lesions can be seen in the mouth, esophagus, crop or nasal passages. If salivary ducts are blocked inflammation may occur in the lower jaw or under the tongue. Vitamin A deficiency predisposes to secondary infection in the sinuses by bacteria or fungi, and Amazon parrots being yacos very prone to this problem. They may also be affected eyes (inflammation and accumulation of pus).

In mild cases of vitamin A deficiency, especially parakeets, initial symptoms are increased water consumption and urine production increased as a result of an alteration (squamous metaplasia) of the ducts and gastrointestinal tract.

- Hyperkeratosis: thickening of the skin of the fingers. More common in Amazon parrots and canaries. These changes predispose to infection, forming the typical abscesses (nails).

- Altered reproduction: eggs with rough shells, egg freezing, decreased sperm production, and so on.

Some species of birds (Amazons, yacos, eclectic) have a higher requirement for vitamin A than others. Certain parasites, like giardia and worms, can decrease the amount of vitamin A available for the bird.

Signs of vitamin deficiencies can become very obvious, but sometimes can be confused with other diseases: tuberculosis, tumors, bacterial infections, etc..

Vitamin A is connected with other vitamins:

- Vitamin K: Excessive doses of vitamin A are deficient in vitamin K.

- Vitamin E: Prevents the destruction of vitamin A in the intestine.

- Vitamin C deficiency symptoms of vitamin C improve with the administration of vitamin A.

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