Nutritional Diseases of Pet Birds
Proper nutrition for companion birds historically has been and continues to be a concern for avian veterinarians, aviculturists, and owners. Although avian nutrition has greatly improved in the past decades, nutritional disease is still common in pet birds. The availability of formulated diets and hand-feeding formulas have been pivotal in improving avian nutritional health, but many birds are still fed inadequate diets. The two most common reasons for malnutrition in companion birds are feeding diets that allow the birds to choose what they want to eat (either mixtures of seeds/nut and pellets, or table foods the owner considers healthy) and feeding pure seed or seed-based diets. Feeding a mixture of pellets and seeds is also common, resulting in selective eating and consequently inadequate nutrient consumption.
Many of the illnesses seen in pet birds have their basis in malnutrition. This includes hepatic disease, renal insufficiency, respiratory impairment, musculoskeletal disease, and reproductive problems. For additional information on nutrition in pet birds, see Nutrition in Birds.
Obesity is common in companion birds. High-fat diets (seeds, nuts, and many table foods), overabundance of food, and a sedentary lifestyle are all contributing factors. Obesity is typically defined as a bird being 20% over ideal weight, with a body condition or keel score of 4 out of 5 (see Physical Examination). Galahs, macaws, Amazon parrots, and quaker parrots are prone to obesity. Clinical signs may not be evident but include lameness (pododermatitis and/or arthritis) and respiratory issues from excessive abdominal fat.
Obese birds should be converted to a pelleted diet with portion control. Exercise should be encouraged by providing a larger cage with multiple food bowls around the cage to encourage movement. Rope or spiral rope perches will encourage climbing and balance. A flight cage outdoors should be provided for flighted birds, and walking or climbing stairs encouraged for nonflighted birds. Obese birds are more prone to arthritis, fatty liver disease (hepatic lipidosis), atherosclerosis, and cardiac disease.
Vitamin A plays an important role in avian health and is crucial for a healthy immune system. Hypovitaminosis A causes squamous metaplasia of epithelium within the oropharynx, choana, sinuses, GI tract, urogenital tact, reproductive tract, and uropygial gland as well as hyperkeratosis of the feet. All-seed diets and even mixed diets of ½ seeds and ½ pellets are deficient in vitamin A.
Clinical signs are nasal discharge, sneezing, periorbital swelling, conjunctivitis, dyspnea, polyuria, polydipsia, poor feather quality, feather picking, and anorexia. Birds may have absent or blunted papilla of the choanal slit. White plaques (hyperkeratosis) may develop in and around the mouth, eyes, and sinuses. In chronic epithelial conditions (eg, pododermatitis, sinusitis, and conjunctivitis) that have been refractory or recurrent, often vitamin A deficiency is the primary cause. Birds with reproductive disease on poor diets should be considered deficient.
Treatment involves treating secondary infections, supplementing with vitamin A, and converting the bird to a good quality pelleted diet. Parenteral vitamin A can be given (100,000 U/kg, IM). Vitamin A precursors, such as spirolina, sprinkled daily over the food are a safe way to supplement diets deficient in vitamin A. The diets of all pet birds should be evaluated for vitamin A content.
Goiter, or thyroid hyperplasia, occurs in budgerigars on all-seed diets deficient in iodine. This condition is no longer common because of the availability of pelleted and fortified diets. Classic signs are respiratory stridor, wheezing, or clicking due to the pressure of the thyroid on the syrinx. Lugol’s iodine (1 drop/250 mL of drinking water) can be used until conversion to a pellet or fortified seed diet is accomplished and clinical signs have subsided.
Seed-based diets are well known for their calcium:phosphorus imbalance and amino acid deficiencies. Sunflower seeds, which tend to be selected preferentially by many psittacines, are low in calcium, deficient in essential amino acids, and high in fat. Safflower seeds are actually higher in fat content than sunflower seeds, contrary to popular belief, and also contain inadequate amino acids and calcium.
Nutritional secondary hyperparathyroidism can occur in young and older pet birds. Because the calcium to phosphorus ratio in most seeds is poor (high phosphorus and low calcium), birds on a seed diet become seriously depleted. The effects of a calcium-deficient diet are often compounded by inadequate exposure to unfiltered sunlight in birds housed indoors, resulting in vitamin D3 deficiency as well. In young birds, especially African grey parrots, hypocalcemia may present as osteodystrophy, with curvature and deformation of the long bones and vertebrae. African grey parrots are also prone to an acute hypocalcemia syndrome that is associated with both hypocalcemia and hypovitaminosis D3.
Clinical signs include weakness, ataxia, tremors, depression, seizures, and pathologic fractures. In reproducing birds, eggs are often thin-shelled, egg production and hatchability are decreased, and embryonic death occurs. Calcium deficiency can lead to cessation of egg laying, egg binding, or cloacal prolapse. Diagnosis is based on decreased total and ionized plasma calcium levels and radiographic evidence of decreased bone density or pathologic fractures. Serum 25-hydroxycholecalciferol levels can also be measured and are usually low.
Treatment is supportive care, calcium and vitamin D supplementation, conversion to an appropriate diet, and exposure to ultraviolet light, preferably natural sunlight. If pathologic fractures are present, splinting or bandaging may be necessary, along with cage rest, NSAIDs, or analgesics. Initial treatment should consist of calcium gluconate (100 mg/kg, IM).
Pet birds should have exposure to natural sunlight when possible. Owners should provide an outdoor cage that provides opportunities for climbing and/or flight and access to direct sunlight. Birds should be monitored closely when outdoors, even in a cage, because many predators can injure a pet bird through cage bars.
Iron storage disease refers to disease that occurs with excessive iron accumulation in the liver. Hemachromatosis is reserved for cases associated with actual pathology. As iron levels within the liver increase, hepatic lysosomes are damaged and release ionic iron, resulting in oxidative damage to membranes and proteins. Iron storage disease is common in mynahs and toucans, and in certain zoo birds such as birds of paradise; it has been occasionally reported in pet psittacine species, particularly lories. Iron storage disease is associated with excessive intake of dietary iron. However, not all birds are affected when fed similar diets, and stress or genetic factors may also play a role. Certain foods rich in vitamin C, such as citrus fruits, increase dietary iron uptake. Current dietary iron recommendations for toucans and mynahs are <50–100 ppm.
Clinical signs are anorexia, weight loss, depression, distended abdomen with ascites, dyspnea, and biliverdinuria. The liver, spleen, and heart are the most commonly affected organs. Circulatory failure, ascites, and hypoalbuminemia are often seen clinically. Diagnosis is by liver biopsy.
Treatment includes periodic phlebotomy, iron chelation, and dietary modification. Recommending low-iron diets routinely for pet mynahs and toucans is prudent (commercial formulas are available). Foods high in vitamin C should be avoided. Supplementation with chelators such as tannins, fiber, and phytates has been suggested.
In addition to the well-documented nutritional deficiencies in diets designed for psittacines, described above, the following dietary concerns should also be noted: 1) the potential sensitivity of individual birds to dyes and preservatives added to some seed and pelleted foods; 2) the high incidence of hepatic lipidosis, atherosclerosis, and right-side heart failure in sedentary captive birds consuming primarily seed diets; 3) the occurrence of hepatic fibrosis and cirrhosis secondary to aflatoxicosis from improperly stored seed and pet-grade peanuts; 4) the difference between food provided by well-meaning owners for their birds to eat (table foods, formulated pelleted diet, vegetables, etc) and what the birds actually consume (seed); and 6) the low palatability of most vitamin and mineral supplements added to water, which are not only ineffectual but can lead to decreased water consumption and dehydration.
Foods that owners should be advised to avoid feeding their birds at any time are chocolate, caffeinated beverages, alcohol, junk food (salt, sweets), milk products, onions, avocados, and apple seeds.
Wild birds spend many hours a day foraging for food. Captive and pet birds usually consume all of their caloric needs at one food bowl, with very little time or energy expended. To promote a healthier lifestyle for companion birds, foraging opportunities should be provided that increase activity, promote a healthier diet, and stimulate birds intellectually. Owners need to provide a cage large enough for the bird to climb and play in, with rope or other perches that stimulate activity and balance. Multiple small food bowls should be placed throughout the cage to encourage movement. Foraging toys with food bits promote activity as well. An outdoor flight cage that allows natural sunlight and increased activity is ideal.