N. Harcourt-Brown, BVSc DipECAMS FRCVS
Harrogate, N. Yorkshire, UK
It is a sad fact that the majority of pet parrots are fed on nutritionally deficient diets. There are several factors that encourage this to happen but these are mainly due to the ignorance of many bird owners and also owners of pet-shops.
The majority of pet psittaciforms are given a seed-based diet to eat. Seeds fall into two categories: sunflower seed, peanuts and pine nuts, are large seeds that contain a lot of oil. Small seeds such as safflower, hemp, millet and canary seed contain mainly carbohydrate. Seeds are high calorie, low in calcium with a poor Ca/P ratio, low in most vitamins, have either low protein content or a limiting essential amino acid, usually lysine or methionine. Seed based diets have little to recommend them nutritionally but they are easy to store and do not deteriorate visually. They are also universally attractive diet to many parrots. In many pet shops the seed quality is poor, is stored for an unspecified time and in unspecified circumstances and is often seed that has failed to make the grade as fit for human consumption. The seed based diet is almost never subjected to nutritional analysis and if an analysis of a mixed seed diet is offered it is usually book-based.
Although many owners attempt to feed a varied diet, their birds usually select an unbalanced seed-rich diet. Some Grey Parrots eat nothing but sunflower seed. Also most birds are offered far too much food further enabling the bird to eat only the seeds that it wants. A Grey Parrot will maintain its body weight on one tablespoonful of sunflower seed per day.
The onset of clinical signs of a dietary deficiency is based on the lifestyle of the parrot: productive birds show more dramatic signs more quickly.
As most parrots' diets are deficient in several vital nutrients the bird is usually presented with a multitude of subtle problems and just because one deficiency is more obvious, such as osteodystrophy in a growing baby parrot, it does not mean that this will be the only deficiency.
Finally, every client says that they feed their birds on 'only the best,' never believe them. Rely on your clinical impression, you will usually be correct.
Vitamin A deficiency causes squamous metaplasia of the mucous membranes affecting oropharynx, respiratory, reproductive and renal tracts. The abnormal keratinisation blocks the ducts of the glands causing abscesses in the salivary and mucus glands. Carotenoids produce much of the feather colour in parrots. In vitamin A deficient birds the yellow, orange and red colours are much duller and the green plumage (made of yellow carotenoid and blue caused by scattered light) is affected too.
Vitamin A is formed in the bird by converting beta carotene from a vegetable source: fresh vegetable such as carrot, maize or sweet corn, green beans, celery, apricots, etc.
Vitamin E deficiency is commonly seen and occurs because storage of seed for long times allows the oils to become rancid and the vitamin E to deteriorate. Generalised weakness due to myopathy will occur and is also worsened by selenium and sulphur containing amino acid deficiency.
Vitamin D3 is often deficient in pet birds. Various vitamin D precursors are metabolised within the skin by ultraviolet light to form Vitamin D3. Glass tends to filter out u/v light form sunlight. As the calcium to phosphorus ratio in most seeds is poor (high phosphorus and low calcium) many parrots become seriously depleted. In birds that are laying eggs or still growing the problem is quickly seen as egg-binding in the former and osteodystrophy with bony deformity in the latter. Grey Parrots are very prone to calcium deficiency, which manifests as convulsions or the bird will suddenly fall off its perch. Their ionised calcium (and often total calcium) level is low as is their Vitamin D3.
B vitamins are also deficient in a seed based diet and although these vitamins are made in the gut the birds do seem to get signs of deficiency that could be due to deficiency: poor skin and feather quality, dermatitis, and fatty liver problems.
Vitamin K deficiency is seen in Fig Parrots but is not usually identified in other species. However if a broken blood feather or bleeding claw continues bleeding it is worth considering in any parrot.
Most seed based diets are deficient in some essential amino acids. These are usually lysine and methionine. In productive birds, moulting, egg-laying and growing birds, protein deficiency is obvious. In adult non-productive birds it is less so but these birds often have great difficulty in responding to disease or injury.
Iodine is usually low in seed. This leads to a lack of thyroxine, which controls the basal metabolic rate and also initiates moulting.
Typical signs of nutritional deficiency in adult parrots.
Poor integument quality: flaky beaks and scaly skin plus softening of the claws and beak allowing overgrowth
Poor plumage, both in form and colour
Delayed or incomplete moult
Convulsions or muscular weakness
Lethargy and inability to fly
Upper respiratory tract disease plus conjunctivitis
Reduced resistance to disease
Inability to breed: lack of libido, egg-binding, infertile eggs, deformed baby birds
Most birds have specific feeding times and do not usually need to eat outside them. They feed in the morning and in the evening. Parrots are vegetarian birds. They should be fed a balanced vegetarian diet and the diet should be in a form where it is difficult for the bird to be selective. The food should be fed in a quantity where the bird is kept slightly hungry and especially where it is keen to eat its next meal. Parrots (and other birds) are similar to many humans; they will eat a favourite food when they aren't hungry and will continue to do so. Unfortunately many people see this as a reason to feed the bird large quantities of this particular food.
A balanced vegetarian diet can be made from a mixture of fruit, vegetables and pulses. Pulses is a term used for peas and beans. The pulse mixture that I use consists of equal parts of mung beans, black-eyed beans, chickpeas and marrowfat peas with half a part of soya beans.
I take equal quantities of apple and raw carrot and chop them into bean-sized lumps in a food processor. To this I add an equal quantity of pulses that have been soaked for 24 hours and then thoroughly washed and drained. It is also possible to gently cook the pulses rather than soak them. I then chop the whole mixture into pieces about 2-3mm in size. I add a suitable vitamin and mineral supplement and mix into the food.
This is a low calorie well-balanced food and is suitable to feed throughout life to the larger parrots. It is also suitable for the birds whilst rearing their chicks. This diet is too low in calories for small parrots such as conures and parakeets or during the winter if the parrots are kept outside without heat in the UK. These birds should have some seed added to their diet. Macaws seem to need more oil in their diet and they should have some large nuts such as walnuts and Brazil nuts.
Birds always tend to eat selectively. It is possible to prevent this by being careful about the amount of food that is fed each day. The birds should be fed twice daily. The apples/carrots/pulses mixture is fed in the morning. If it is finished, then later in the day extra food can be provided in the form of more mixture if the birds are breeding or seeds and nuts in birds that require them, especially in cold weather when the nights are short.
The vitamin and mineral supplement can be changed when the birds are breeding.
There are a number of water-soluble products that are sold to supplement vitamins and minerals, especially calcium. Even when the manufacturer's instructions are followed these products do not prevent deficiency. They should not be used or relied upon.
All parrots should be provided with grit. The grit sold for pigeons is suitable. Parrots start to take it as soon as they are weaned.
The big drawback with this fresh vegetarian diet is that it can ferment if left for a long time in hot temperatures. Pelleted diets are less prone to this. All-in-one pelleted diets are also the most convenient and suitable way of feeding single pet birds. There are a number on the market in Europe and the USA. Initially owner and parrot acceptance may be low, primarily because many birds do not like them. The client must be educated and they must persevere. Do not attempt to force an ill bird to change diet and do not force the bird to eat the new diet by starving it. Young adventurous birds will often make the change quickly; older birds do not. It is possible to introduce the pellets into the normal diet and slowly change the quantity being offered. Over a few weeks the bird will end up eating 100% pelleted food. However it takes a 'good' owner to make this work. If the owner is sure that the bird will not eat its new diet then it is best for the vet to take control. I admit the bird and tell the owners that I am going to keep it for a week. I then place a small quantity of the pellets in its food bowl. If possible I weigh the bird. I watch its droppings to see if the faecal portion disappears. Its gut is then empty and if it is not eating the pellets it has to be fed. I usually use a baby bird food made by the manufacturers of the pellets and give this two to four times daily by crop tube. The amount of supplementary feeding depends on weight loss of the bird. Weight loss is not common and the bird usually requires feeding only twice daily. It is rare for the bird not to be eating the pellets by day five.
I tell the owners that the pellets are to replace the seed-based diet but that the bird still needs some fruit and vegetables and it can have its treats-pizza crusts, chips, nuts in small quantities. The pellets must remain as 80% of the diet.
Treatment of chronic vitamin deficiencies is by dietary change. However owners should be made aware that full improvement will take a year. For acute problems, such as grey parrots with convulsions more aggressive treatment is required. I tend to avoid using injectable multi-vitamin supplements. In my experience they are a dangerous.
Convulsant grey parrots or birds that are egg-bound should be given subcutaneous 10% Calcium borogluconate and be fed a baby bird food (10 mls for a grey parrot) with added calcium (Nutrobal, VetArk UK) by crop tube. The bird should then be put somewhere quiet and warm. Most birds lay their egg within a few hours.
1. Scott PW (1996) Nutrition In: The Manual of Psittacine Birds (P Beynon, N Forbes, M Lawton eds.). BSAVA Publications, Cheltenham UK pp.17-26.
2. McWhirter P. (1994) Malnutrition In: Avian medicine: principles and application. (BW Ritchie, GJ Harrison, and LR Harrison eds.). 1st ed. Blackwell Science, UK. pp. 842-861.
A (less expensive) reprint of this edition, with the pharmacology chapter updated but without the anatomy of the cockatoo, is distributed by HBD International Incorporated, 220 Congress Park Drive, Suite 232, Delray Beach, Florida 3345.