Abstract
Stunting is a problem frequently seen in aviculture today. Many aviculturists, for a variety of reasons, are not able to recognize this progressive and insidious development in their hand fed babies until much more serious problems have evolved. Stunted birds are most likely immunologically weakened and susceptible to infectious disease at a greater risk than normally developed birds. Permanent physical deformities may plague the bird for the remainder of its life including inadequate or deformed skeletal systems, beak deformities, inadequate psychological development, damaged or poorly developed internal organ systems, and questionable reproductive capabilities. This human induced metabolic condition is the result of one or all of the following reasons:
1. Nutritionally deficient diets
2. Insufficient amount of food:
Low volumes of formula Inadequate numbers of feedings per day
3. Medical condition preventing the normal digestion and absorption process (low grade toxicity i.e. visceral and articular gout, vitamin D3 toxicity; bacterial and fungal infections [ e. coli, candida], viruses i.e. Papova, and burned crops).
There are three stages of stunting:
Early stage: these birds are not being supported nutritionally (or possibly medically) to allow them to reach their genetically predestined size. If their condition is recognized in time, their deficient development can be corrected and they will continue to achieve their normal expected size. Early detection of stunting can be determined by experienced hand feeders who review their birds' weight records daily and compare them with previously recorded normal growth data for the species being hand fed. Unfortunately, inexperienced hand feeders may not keep weight records or have no data to compare their birds' weight. Consultations with other breeders who have bred the specific species you are feeding will be helpful to newcomers who otherwise might not have the ability to catch stunting in this early stage.
Intermediate stage: characteristically causes the head and feet to remain close to normal size with the body size affected. The body is stunted in both length and girth. The photo from the Emperor Valley Zoo in Trinidad is an example of the classic mature stunted bird - a mature Blue and Gold Macaw with a body the size of a medium Amazon. Most of the intermediate stage birds do survive. Not being adequately fed produces bone structure that does not reach its genetic potential and is often accompanied by distortion of the skeleton (see Hyacinth Macaw x-ray photo). The majority of this article will deal with this group of birds. The accompanying photo ( courtesy of Brian Speer, D.V.M.) shows a grossly underweight Hyacinth Macaw that was 570 grams at 68 days old. This Hyacinth should have been over three times that weight (1500 to 1600 grams) by this age. The hand feeder sought veterinary care when he had observed a sudden onset of weakness and poor crop motility, both of which were the cumulative effects of chronic stunting. Although this is an example of Advanced Stunting Syndrome, this bird was rehabilitated and did not outwardly show the signs of stunting when it was weaned. Another example of intermediate stunting is the Lynn Dustin, D.V.M., photo of the Blue and Gold Macaws at 35 and 37 days old. They weighed 260 and 160 grams respectively. The 37 day old weighed less than the 35 day old due to a ventricular septal defect in the heart. Both birds gained weight on an improved diet. Many of the common characteristics of stunted birds, i.e. thin, bony wings, conical shaped head and abnormal feathering, are present in this photo.
Advanced stage: these birds are so extremely underfed that they are grossly deformed. Severe nutritional problems have occurred which might also be accompanied by opportunistic infections such as candida or E. coli. These birds generally die before the bird reaches the feathering stage. The photo of the advanced stunted Blue and Gold Macaw is a 21 day old weighing 34 grams; this would be normal for a 2 day old. Veterinarian care was not sought in time. This bird died the next day.
Internal skeletal distortion is shown dramatically in the Hyacinth Macaw x-ray in this article. The volume of food was not the problem with this bird. He was eight weeks old and weighed 1200 grams. Normal weight for this age would be in the 1390 to 1560 range. James Harris, D.V.M., describes the bird as follows: "This is an example of nutrition related osteoporosis. Insufficient calcium and vitamin 03 in the diet resulted in bone that was unable to support the weight of this rapidly growing macaw chick. The spinal column has collapsed as have the rib cage and sternum. The bird died of asphyxiation from its inability to expand its respiratory system. There were also fractures of the long bones.''
Diets high in protein and/or vitamin 03 have been shown to be a problem in macaws. African greys need more calcium and vitamin 03. All current hand feeding diets are probably deficient or excessive in some nutritional area. Parrots are specialized feeders. Expecting one generic hand feeding diet to nutritionally satisfy multiple species of parrots is unrealistic. As more data is collected on optimal growth rates for specific species of birds, we will be able to tailor individual diets to match their specific needs. Commonly used generic diets do not attest to their nutritional value as much as to the incredible tolerance range of parrots.
Watered down diets are just as much a problem as high concentrated diets. Thinning down diets with extra water or fruits and vegetables changes the nutritional basis.
Stunting can occur in any species, however, the likelihood increases in the larger parrots such as Amazons, cockatoos and macaws because of the larger volumes of food required for normal growth. In the hands of inexperienced hand feeders, these birds are often weaned many weeks before nature intended. For instance, 20 to 24 weeks is our average to wean a Hyacinth Macaw. But I've seen "weaned" birds that are 12 weeks old with the classic stunted macaw symptoms, normal sized head and feet with a small body size. This gives the appearance of a huge head, drawing attention away from the small body. Their weights were also less than expected for normal.