How I diagnose and manage nutritional disease in birds (Proceedings)
Proper nutrition for companion avian species has long been and still is a central focus of avian veterinarians and aviculturists. While nutrient requirements have been precisely defined for "economically important" species such as poultry, the body of knowledge for companion species backed by scientific exploration is lacking in comparison. Quite honestly, the exact nutritional requirements for companion psittacine species are still not known. However, we can still make educated estimates of their nutritional needs based on an understanding of the biology/ecology of their free-ranging conspecifics, basic biomedical sciences, information available regarding poultry nutrition1 and the most current concepts of companion avian nutrition.
Currently, high quality, state of the art commercial diets are available for various age groups, activity levels, reproductive status2 and even birds with specific health issues such as liver or kidney disease. Unfortunately, just like many humans, birds do not always have the ability to choose a balanced diet if offered unhealthy items such as sour cream and onion potato chips or red-velvet cake. As a result, diseases related to inadequate or inappropriate diets are arguably still common occurrences. This article will review selected nutritional diseases in avian species including their clinical signs, diagnosis and treatment.
Hypovitaminosis AVitamin A plays a crucial role in the health of avian species. It is necessary for vision, immune function, normal function of secretory tissues and growth and differentiation of epithelial cells within the respiratory tract and small intestine.3-7 Chronically low dietary vitamin A usually results in respiratory tract disease, poor feather quality and poor growth. Squamous metaplasia of epithelium within the oropharynx, choanal, sinuses, gastrointestinal tract, urogenital tract and uropygial gland and hyperkeratosis of the feet and gout may also occur.3-5 Susceptibility of birds to sinus infections in conjunction with a deficiency of vitamin A appears to be associated with blunting of the papillae of the choanal slit, which suggest inadequate differentiation of the lining of epithelial tissue lining the sinuses.
Minimum vitamin A requirements have been elucidated for various poultry and waterfowl species; however, the exact dietary requirements necessary for maintenance or toxicity in companion avian species is not known.8 Most likely the cause of hypovitaminosis A in psittacine species is the feeding of a seed based diet. Seed mixtures commonly fed to companion birds have concentrations <30 µg/kg and birds maintained on these diets often develop signs of hypovitaminosis.8
Clinical signs include white plaques, abscesses or focal kertinaceous granulomas in the oropharynx, blunting of chaoanal papillae, nasal discharge, periorbital swelling, dyspnea, polyuria, polydipsia, poor feather quality, feather picking and anorexia.5 Diagnosis is usually based upon dietary history, physical examination and cytology of the respiratory tract.
Converting the bird to a good quality pelleted diet is crucial to correcting dietary deficiencies. Immediate treatment of problems associated with vitamin A deficiency consists of the removal of plaques or abscesses, appropriate antimicrobial therapy, and supplementation of vitamin A both parenterally (maximum 20,000 IU/kg IM)9 (Aquasol A, AstroZeneca LP, Wilmington, DE) and orally as needed. Estimates of the requirements of vitamin A for maintenance is 600 µg/kg or below.8 However, be careful not to over-supplement with vitamin A as the range between deficiency and excess is very narrow compared to other vitamins.8 Many vitamin A supplements that are commercially available prescribe levels of supplementation those results in high levels of vitamin a equivalent to 7,500-30,000 µg/kg in the diet. Additionally, some commercially available pelleted diets are over formulated with vitamin A levels between 1,500-6,000µg/kg diet.8 Koutsos et al demonstrated dietary concentrations ≥ 3,000 µg vitamin A/kg of diet can cause toxicity.8 Signs of vitamin A toxicity include poor feathering, pancreatitis, multifocal accumulation of lymphocytes within the duodenal lamina propria, hyperexcitability and exaggerated vocalizations.8 Converting the bird to a good quality pelleted diet is also crucial to correcting dietary deficiencies.