Bird and Exotic Animal Hospital, Onderstepoort Veterinary Academic Hospital, South Africa
Malnutrition is the underlying cause of many of the disease conditions seen by the avian practitioner. Parrots in their natural environment are herbivores that utilise a very wide variety of plants throughout the year, ingesting fruit, seeds, berries, leaves, buds, and roots. There are a few exceptions such as the nectar-eating lorikeets and the black cockatoos that eat a majority of palm nuts. The average captive parrot receives a much more limited diet than their wild cousins and misconceptions abound regarding their nutritional requirements. The practitioner should be able to recognise malnutrition from the history as well as by its clinical manifestations and give advice on the correct diet and how to encourage the bird to convert to the new food.
The majority of uneducated owners offer their parrots a large amount of fatty seed and far too little fresh plant material. This diet is deficient in at least 32 nutrients including vitamins (B vitamins, biotin, vitamin D3, vitamin K, folic acid and the vitamin A precursor, β carotene), minerals (calcium, phosphorus), trace elements (selenium, copper, iron, zinc, iodine), protein, fibre, and omega 3 fatty acids.
Birds unfortunately do not demonstrate nutritional wisdom as in "he eats what's good for him" and will preferentially select high-energy lipid-rich seeds and carbohydrate-loaded fruit. As it is not possible to offer captive parrots the variety of food that they would eat in the wild, formulated diets have been developed to meet their nutritional needs. The advent of high-quality formulated diets has markedly reduced the incidence of nutritional disorders in companion birds but not all diets are created equal. Extruded diets prevent the parrot from selecting out favoured food items as each pellet is nutritionally balanced.
Oversupplementation can be as dangerous as nutritional deficiency and birds on a formulated diet should not be given extra supplements. Vitamin A and D are the two most commonly oversupplemented. Excess vitamin D can lead to renal calcinosis and widespread calcification of the soft tissues, and excess vitamin A to epithelial damage, pancreatitis, hypovitaminosis E, and reproductive failure.
The Recommended Diet
There is limited research available on the nutritional requirements of parrots, but generalisations can be made from the established requirements of poultry.
Current recommendations are that approximately 60% of the diet should be a formulated product, with the addition of vegetables, fruit, and a limited amount of seeds and nuts. Certain species have more specialised requirements - the large macaws, for example need higher fat in the diet which can be achieved by the addition of tree nuts. Eclectus parrots have increased vitamin A requirements. The addition to the diet of β carotene from green and orange vegetables assists in this regard. Eclectus parrots should have a minimal amount of seed in the diet and may also be sensitive to colourants and preservatives in the formulated diet. Specialised fluid diets are available for the nectar-eating lorikeets. Daily access to unfiltered sunlight is also important for effective calcium metabolism and feather health.
Clinical Manifestations of Dietary Imbalances
The site where signs of malnutrition are often noted first. Hyperkeratosis of the epithelial tissues is commonly seen in vitamin A or biotin deficiencies and is manifested by:
Overgrowth of beak and nails
Poor quality of beak and nails - flaking, chipping and breaking
Retained pin feathers that may be painful for the bird
Poor quality feathers - scruffy, inflexible, break easily, abnormal moulting
Abnormal feather colour (e.g., black feathers on green or blue birds, pink feathers on African Greys)
Hyperkeratotic lesions on the plantar surfaces of the feet, leading to pododermatitis
Conversion to a formulated diet and potentially the addition of red palm fruit oil, an excellent source of β carotene, vitamin E and carotenoids is recommended.
Gastrointestinal Tract (GIT)
The normal bacterial flora of the psittacine GIT is completely G+. A faecal Gram stain may be used to evaluate faecal flora. Increased numbers of G- bacteria indicate an imbalance which may be an indication of malnutrition or liver disorders.
Fatty liver syndrome is associated with an accumulation of excessive abdominal and hepatic fat. Lipid infiltration weakens the hepatic cellular structure and results in hepatomegaly and a friable liver. The enlarged liver compromises the airsacs and may cause exercise intolerance and even death from hypoxia. Hyperlipidaemia and hypercholesterolaemia are often seen. Older, obese parrots on seed-based diets are predisposed and Amazon parrots seem particularly prone to this disorder. Feather discolouration, changes in faecal flora, and liver dysfunction indicated by raised bile acids can be indicators of hepatic lipidosis. Affected birds may display bleeding tendencies, depression, and anorexia. Slow, controlled weight loss, increased exercise and conversion to a proper diet are indicated. Supplementation of silymarin (from the herb milk thistle) in the food has proven empirically effective as an antioxidant and promotor of the growth of new, healthy liver cells.
Hyperkeratosis of epithelial surfaces and loss of function of the cilia occur. Desquamated epithelial cells may develop into rhinoliths, tracheal and airsac obstructions. These areas easily become secondarily infected with bacteria and fungi such as Aspergillus. Clinical signs include:
Blunting or loss of choanal papillae
Airsacculitis and pneumonia
Blocked sinuses with rhinoliths
Overinflation of airsacs on radiograph
Deformity of nares and destruction of nasal septum
Atherosclerosis occurs in birds on high-fat diets, especially if they are afforded little opportunity to exercise. The process is that of cholesterol deposition on the inner arterial walls with associated inflammation and fibrosis. In advanced cases the plaques may be visible as an increased radiopacity of the vessels near the heart.
Vitamin A, antioxidant, and omega 3 fatty acid supplementation is beneficial as part of the treatment. Anecdotally red palm oil has also provided beneficial effects.
Some birds with neurological disease (opisthotonus, ataxia, hindlimb weakness) respond empirically to supplementation with vitamin E and selenium and also to B vitamins. Encephalomalacia, potentially related to thiamine deficiency, has been recorded in an African Grey parrot.
Hypocalcaemia occurs either due to a calcium deficiency in the diet, an incorrect Ca/P ratio in the food, or to lack of access to natural sunlight. Parrots spread oil from the uropygial gland over the feathers. Provitamin D3 is converted to active vitamin D3 by the action of the sunlight and is then ingested by the bird in subsequent grooming sessions.
Three syndromes occur: osteodystrophy in growing chicks, hypocalcaemic tetany in African Grey parrots, and egg binding in reproductively active hens. Diagnosis is by clinical exam and blood calcium levels; treatment with parenteral calcium gluconate is indicated.
High fat and sugar diets in non-breeding companion birds are suspected to be involved with the overly stimulated, hormonal bird that may display aggression, inappropriate sexual behaviours like masturbation and regurgitation for a toy or favoured human, feather plucking, etc.
Reproductive failure is intimately associated with a large number of dietary imbalances.
Conversion to the Correct Diet
It can take a great degree of perseverance and patience to convert a parrot to a healthy, balanced diet. Parrots can develop marked preferences for foods of a certain taste, texture or colour and can be extremely resistant to trying new foodstuffs.
The following tricks can be tried during the conversion process:
Mix the old and the new food, gradually over weeks decrease the amount of the original diet. Tantrum type behaviour with the bird screaming, throwing food, etc. can be expected.
Allow the bird to see others eating the new diet.
Remove all perches except the one by the food bowl, forcing the bird into proximity with the food.
For flock birds such as cockatiels, place a mirror on the floor and scatter food over it.
Attempt to hand feed the new diet as a "treat."
Moisten the extruded pellets with fruit juice.
Feed the old diet for 30 min, morning and evening, and feed the new diet in-between.
When all else fails, admit the bird to hospital and convert there. Birds will often more easily accept the new food in a novel environment.
Weigh the bird regularly and return to the original diet if more than 10% of the original body mass is lost.
Nutritional disorders are extremely commonly seen in avian practice. The veterinarian should be able to easily diagnose them on history and clinical signs and address them by correcting the diet and treating any clinical manifestations seen. The advent of formulated diets such as extruded pellets has markedly reduced the incidence of nutritional disorders in companion birds and should be recommended for all avian patients. Conversion to a balanced diet may be an extended process and hospitalisation may be necessary to facilitate the change. By offering sound nutritional advice, the veterinarian provides a service critical to the long-term health and wellbeing of their avian patients.
1. Harrison GJ, Lightfoot TL. Clinical Avian Medicine, Vol 1. Palm Beach, FL, USA: Spix Publishing, Inc. 2006: 85–212.