Vitamin A is one of the fat-soluble vitamins. It is an antioxidant, helps in the growth and repair of tissues, and is important for proper functioning of the eyes, hearing, skin, bones, and mucus membranes. It is found in many fruits and vegetables but not in many seeds. A deficiency in Vitamin A, called "hypovitaminosis A," is all too common and potentially disastrous when birds are fed seed-only diets. When feeding an all-seed or mostly-seed diet, the malnourishment that results weakens a bird, making it more susceptible to bacterial, viral, or fungal infections. These secondary conditions are, if left untreated, ultimately responsible for the demise of the bird. Hypovitaminosis A is easily preventable in companion birds if they are fed fruits and vegetables high in Vitamin A.
How does a deficiency in Vitamin A cause disease?
Vitamin A has its greatest effect on tissues that line the respiratory, digestive, and reproductive tracts. When Vitamin A is low or absent from the diet, these cells undergo changes that prevent the secretion of mucous, thus destroying a critical line of defense against bacterial invasion. The microorganisms can then enter, and begin multiplying. The end result depends on what body system is primarily affected. Most often, it is the respiratory system.
Visually, one will often see small white patches or "plaques" in the mouth and on the tongue. The infection progresses and these plaques begin to swell and abscess, eventually becoming so painful the bird ceases to eat. Depending on how large they become, these abscessed plaques can block the choanae. This leads to labored or open-mouth breathing - something you never want to see in a bird. A profuse nasal discharge and severe swelling around the eyes will follow, also a result of obstruction of the choanae. The swelling may reach the point where the bird will not be able to swallow, preventing any nutrition from reaching the body. From here, the microorganisms move throughout the body with devastating results.
What are the other signs of hypovitaminosis A?
Symptoms range from obvious to obscure and include any of the following: sneezing, nasal discharge, wheezing, crusted and/or plugged nostrils, lethargy, depression, diarrhea, egg binding and dystocia, tail-bobbing, lack of appetite, emaciation (severe weight loss), poor feather color, swollen eyes, ocular discharge, gagging, foul-smelling breath, white patches or a "slimy" appearance to the mouth. Most of these imply your bird is very sick and needs immediate attention. These signs do not develop suddenly, but happen over the course of several weeks to months.
What is the treatment of hypovitaminosis A?
Vitamin A supplementation will need to begin immediately. Other treatment depends on what system is involved. Since the major problem and most threatening condition is usually the microbial infection secondary to the lack of Vitamin A, the infection must also be treated immediately and aggressively. If diagnosed and treated early, the bird's illness can usually be cured without long-lasting effects. Treatment will often involve a period of hospitalization since the bird must receive specialized medical care. Your veterinarian may use an incubator or nebulizer, and the bird may also need to be tube fed and given injections.
How is hypovitaminosis A prevented?
The importance of a proper diet in preventing hypovitaminosis A cannot be overstated. In general, most birds should be fed a diet that consists of 65-80% formulated foods, 15-30 % vegetables, and the remainder fruits and nuts. Some species have specific nutritional needs so be sure to consult with your veterinarian. (See Basic Nutrition in Parrots.) Following are listings of those fruits and vegetables high in Vitamin A, and those low in Vitamin A. Generally, yellow and orange fruits and vegetables, and dark green, leafy vegetables are high in Vitamin A.
| Foods High in Vitamin A||Foods Very Low in Vitamin A|
Broccoli leaves and flowerettes
Roudybush, TE. Nutrition. In Altman, RB; Clubb, SL; Dorrestein, GM; Quesenberry, K (eds.). Avian Medicine and Surgery. W.B. Saunders. Philadelphia, PA; 1997.