Avian Obesity
(and Its Affect on the Respiratory System)

by Dave McCluggage, DVM

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Sitting on the perch, a cockatiel could look totally normal, possibly even well formed and muscular. But, the bird is unable to exercise without significant difficulty in breathing. Why? Because the bird is markedly obese. Obesity is a major cause of disease in cockatiels. Although there are certainly many other causes for exercise intolerance, this column describes how birds become obese and the effect that this excessive fat has on their ability to breath.

The most common cause of obesity is malnutrition, specifically an improper balance of nutrients. Most significant is excessive fat in the diet. Many seeds that are fed to birds contain in excess of 30% fat, and include sunflower, safflower, rape, niger, hemp, and peanut. Birds like high fat seeds and will often select them over any other seeds in the mix. Although specific guidelines are not available, most avian veterinarians believe that the diet should be under 10% fat. Birds that are allowed to selectively eat whatever seeds they choose often will eat mostly high fat seeds, causing the total diet to be about 15-30% fat!

Heredity appears to be another significant cause of obesity. Birds that are obese often produce offspring that are obese. Many of the large birds, upon necropsy, have been shown to be obese, as have their progeny. Other causes of obesity include hormonal (e.g., thyroid deficiency, a rare disease in cockatiels), and a lack of exercise.

Cockatiels carry fat in two locations in the body. They carry large fat deposits under the skin on the sides of their body, and inside the abdominal area. Abdominal fat is not always noticeable from the outside. By parting the feathers on the side, one can observe fat deposits under the skin on the sides of the bird. Fat deposits will cause the skin to appear more yellow than the normal pinkish to white. The skin will feel roly-poly rather than firm. If there is any significant amount of fat on the sides of the bird, there will certainly be large amounts of fat inside the abdomen.

To understand why fat birds are unable to fly, one must first understand how birds breathe. Birds do not have a diaphragm to draw the air in, and their lungs do not expand and contract like mammals do. Instead they have an air sac system. When breathing in air, the air sacs expand to pull air into the body. In avian breathing, the air sacs contract, forcing air into the lungs. Abdominal fat encroaches on the air sacs, causing them to collapse or become smaller. It is common to see birds with air sacs so compressed with fat that they are unable to expand at all. At rest, these birds will breathe normally. With exercise comes an increased demand for air. The bird's respiratory system is viable to meet this demand. There simply is no room in the air sacs for air, and thus, they cannot receive the oxygen they need.

To prevent obesity, the two major causes previously mentioned must be corrected. First, the birds shouldn't never be allowed free access to all the seeds they desire to eat. In an aviary situation, the only way to prevent this is to feed such a small amount of seed that the birds finish the seed portion of the diet in the first hour of the day, leaving less desirable items for later. By limiting the amount of seed fed on a daily basis, the fat content of the diet can also be diminished by lowering the percent of high fat seeds in the diet, say to less than 10% of the seed mix. Feed vegetables, fruits, grains, beans, rice and bird pellets to supplement the diet to insure a balanced diet is being fed.

Secondly, birds must be monitored for obesity. The only way to do this is to catch up birds, weigh them and examine them for fat deposits under the skin on their sides. Recording and monitoring weights over time will eliminate obese birds.

Birds that are always obese, even when on proper diets, should not be bred. This will pass on to the offspring the genetic tendency toward obesity. Obese hens are also more prone to become egg bound when breeding.

Adequate exercise is important for all birds, but obese birds must be exercised cautiously at first. Any significant increase in exercise could kill them. I have seen many birds that were reported by the owner to have died of a heart attack when flying, only to find out at necropsy that the real problem was obesity. Birds should be given large flight cages when not breeding to stimulate exercise.

Obesity is a common problem in cockatiels. It can only be corrected over long periods of time by monitoring weights, feeding balanced diets that are low in fat, breeding birds that do not have a tendency toward obesity, and by moderate exercise.

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