Mark Hagen, MAg
From the University of Guelph, Ontario, Canada.Proper dietary nutrition and food quality are important in fast-growing exotic birds. The right balance of protein (amino acids), energy (fat), solids (water), and other essential nutrients can be achieved with different types of hand- rearing formulas, including homemade recipes, monkey-food- or dog-food- based formulas, and specific commercial formulas. However, some diets are easier to prepare and have a smaller chance of being nutritionally inadequate because of improper mixing and contamination. Digestion in birds is a rapid and efficient process because of the specificity of their digestive organs, which functions to swallow, store, and chemically and physically digest the food.
Copyright © 1992 by W.B. Saunders Company
Key words: psittacine, amino acids, oilseeds, baby formulas, digestion.
Hand-feeding baby birds is a vital part of any successful aviculture operation. Babies from artificially incubated eggs, those removed from neglectful parents, and those pulled at a young age to simulate reclutching of parents all must be hand-fed for 3 to 5 months. Most exotic birds kept in captivity, such as psittacines and the many types of softbills, are altricial. That is, their young are hatched blind, are helpless in food gathering and are unable to thermoregulate. Unfortunately, only limited scientific work on the nutritional requirements of exotic birds has been performed; however, aviculturists, by trial-and-error feeding, have found formulas that successfully raise hatchlings to adult size.
Secretions of the upper gastrointestinal (GI) tract present in regurgitated parental food appear to enhance the growth of parent-fed psittacine chicks over that of incubator-hatched chicks hand-fed the same diet (author's observations). The nature of those secretions and their effect on the food fed to chicks is of continued interest.
Requirements for Growth
Because poultry are precocial, little information on their relatively easy care is directly applicable to parrots, yet their well-researched and published nutritional requirements may act as guide.1.2 Poultry formulas are designed to maximize growth rate, ie, meat production, which is not as critical in exotics as is the proper development of the baby and its long-term health. The following is a discussion of a few nutritional concepts important to the feeding of exotic birds.
Growth curves have been published for only some of the hundreds of different species of psittacines and for very few other exotics.3.4 Individual and sex-related variation in size limit the use of average weight grains to monitor the health of individual babies on a particular diet. Measures of body weight taken each morning before the first feeding are less influenced by residual food from the previous feeding still in the gut of the bird if babies are allowed to eliminate residual food overnight. The time between feedings should be slowly increased as the baby gets older, but any sudden slowdown in digestion is an indication of illness.
Protein and Amino Acids A whole-carcass amino acid composition comparison of the chicken with a small parrot, the budgerigar (Table 1), and the parallel structures of the digestive tract indicate similarity of diet between most psittacines and poultry.5 Studies conducted at the University of California, Davis, showed that cockatiels, grow best when hand-fed a diet containing 20% to 25% dry-matter protein mixed as 7% solids for the first 4 days, followed by 20% to 30% solids, and that their requirement is 1% of the diet on a dry-matter basis.6.7 These percentages are very similar to those in the National Research Council (NRC) growth requirements for broiler chickens,1 supporting use of the NRC requirements as estimates for psittacine growth requirements.
The use of animal protein sources in diets instead of supplementing with limiting amino acids to improve the biological value of plant proteins is controversial. Similar amino acid profiles and protein levels can be achieved with both methods. However, if the animal or fish products are not processed properly, there is greater potential for bacterial contamination. The proximate analysis of the oilseed kernels of sunflower, safflower, and peanut, common food for captive parrots, indicates that they contain very high fat and moderate protein levels when taking into consideration their high caloric densities (Table 2). When comparing the essential amino acid profile for growth requirements in poultry with the levels found in oilseed kernel protein, it appears that lysine and methionine are limiting in all three seeds and threonine is also limiting in safflower and peanut protein (Table 1).
Table 1. Estimated essential Amino Acid Requirements of Parrots and Composition of Three Common Seed Kernel/ Nut Meats
___________________________________________________________________________ Essential Estimated Sunflower Safflower Peanut Budgie Chicken Amino Requirement§ Kernel8.9 Kernel10.11 Meat11.12 Carcass13 Carcass2 Acids* ___________________________________________________________________________ Arginine 6.0 10.0 9.4 11.2 5.9 6.8 Glycine & 5.0 9.3 9.3 10.4 10.8 -- serine Histidine 1.5 2.8 2.6 2.4 2.2 4.1 Isoleucine 3.5 4.5 3.7 3.3(94%)¤ 3.9 3.9 Leucine 6 7 6 6.6 6.2 6.5 Lysine 5 3.9(78%)¤ 3.2(64%)¤ 3.2(64%)¤ 7.1 9.9 Methionine & 3.6 3.7 3.2¤ 2.5¤ -- 4.3 cystine Methionine 1.9 1.8(95%)¤ 1.5(79%)¤ 1.2(63%)¤ 2.2 1.9 Phenylalanine 5.9 7.4 7.2 8.9 6.8 6.7 & tyrosine Phenylalanine 3.2 4.7 4.3 5.0 3.9 3.6 Threonine 3.7 3.8 3.2(86%)¤ 3.1(84%)¤ 4.0 3.4 Trytophan 0.9 1.3 1.4 1.2 0.8 1.0 Valine 3.6 5.2 5.3 4.2 4.8 4.4 No. of limiting 2 3 4 amino acids ______________________________________________________________________________Note. Measurements are grams of amino acid per 16 g of nitrogen.
Although serine, cystine, and tyrosine are not essential amino acids, they are included with essential amino acids because they may spare a portion of the requirement for glycine, methionine, and phenylalanine, respectively. However, under certain conditions the requirement for cystine may not be met by synthesis from methionine, especially if the diet is low in both of these amino acids. Feather protein contains a higher amount of cystine than do other body proteins13; thus, during maximum feather growth in a nestling or molting in an adult, the requirement for cystine may increase. Cystine also serves as the precursor of taurine, which in chickens, and probably parrots as well, is conjugated with cholic acid during the formation of bile.2 Bile formation is induced by fat content, which is high in oilseed kernels and approximately twice as high in most psittacine hand-feeding formulas than in standard poultry starter diets.
Table 2. Proximate Analysis of Seed Kernels or Nut Meat Expressed
as a Percent and Their Gross Energy Value
__________________________________________________________________________ Kernel or Crude Crude Crude Gross Energy Nut Meat Moisture Protein Fat Fiber Ash NFE* (kcal/kg)¥ __________________________________________________________________________ Sunflower+ 4.9 22.4 53.8 3.6 3.0 12.3 7.097 Safflower§ 3.0 23.6 59.3 2.6 3.2 8.3 7.429 Raw peanut 3.6 29.4 53.0 2.4 2.3 9.3 6.829 __________________________________________________________________________Note. Percentage derived from mean values of two samples sent to separate laboratories.
Dietary Energy The dietary energy the bird can use is referred to as metabolizable energy (ME).14 The ME of formulas can very significantly; the NRC for broiler chickens is based on a 3,200 kcal ME/kg diet, whereas oilseed diets are probably around 5,750 to 6,250 kcal ME/kg (based on gross energies of 6,800 to 7,400 kcal/ kg [Table 2] and approximately 85% use). Knowing the daily energy requirements and the ME value of a diet is helpful when formulating vitamin, mineral and protein levels to ensure optimum intake of these nutrients. Birds flying free in the wild have much higher daily caloric needs than sedentary cage birds. Flights to and from the nest to feed offspring further increase caloric needs. Thus, the different caloric needs of captive birds may limit feeding "natural" diets similar to those found in the wild.
Amino acid and the nutrient requirements are often listed in percentages of the diet; however this method of expressing them makes it difficult to compare the amino acid profiles of diets with different energy and protein levels. Expressing amino acid levels as percentages of the protein and in isocaloric portions makes comparisons more meaningful. the protein levels of formulas are often compared without taking into account differences in ME. The first diet scientifically tested on a psittacine had half the fat level now found in most formulas, which results in higher energy values.5 Thus, the levels of vitamins, minerals, and protein have to be increased over estimated requirements, which are based on lower MEs.
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