By Kirk C. Klasing and Elizabeth A. Koutsos
This article is reprinted from a past issue of the Exotic Bird Report, the Project's print publication.
All bird owners are concerned about their birds' nutritional needs and the kinds of food that will meet those needs. A lack of understanding of these issues has resulted in diet fads and rituals that can be unnecessarily expensive and can directly cause illness. An examination of the basic principles of avian nutrition provides perspective on this important subject. Nutrients that must be in the diet for optimum health and productivity are referred to as essential nutrients, and the minimum amounts needed are called dietary requirements. A bird's diet must supply energy to fuel metabolism and must provide the precursors for synthesis of the structural and functional components of cells.
The required levels of dietary nutrients for growth and reproduction are well understood for Galliformes such as chickens, turkeys, domestic ducks and Japanese quail. Based on research, it seems that these four species require similar essential nutrients in roughly the same proportions, but there is a huge range in the amount of different nutrients needed in the diet. For example, a young growing quail chick needs about 24% protein in its diet, but only about 0.0000003% biotin. Rigorous scientific experiments also have determined the levels at which nutrients become excessive or toxic. For some nutrients, like methionine and selenium, toxicities can occur at levels that are only several-fold higher than the required levels. For others, like linoleic acid and vitamin E, toxicities are difficult to induce with common foodstuffs and supplements.
A complete and wholesome diet can be assembled by blending a variety of foodstuffs together so that the final mixture possesses each of the nutrients at a level that is above the dietary requirement (and includes a margin of safety) but below the toxicity level. Obviously, this process requires accurate knowledge of the concentration of nutrients in the food items included in the diet. This information is available for ingredients commonly fed to poultry (Poultry NRC, NAS, Washington D.C.) or consumed by humans (USDA food tables). A simple computer spreadsheet can be used to calculate the correct mixture of food items that will result in the desired level of each nutrient. Specially designed diet formulation programs make the job even easier and are commonly used by professional animal nutritionists. So, with knowledge of nutrient requirements and feed composition, creating a balanced diet can be quite easy.
For exotic birds, the process of formulating diets is an inexact science. There is a lack of documented information about the required and toxic levels of most of the nutrients. While the voluminous and accurate information on poultry may be used as a guideline for exotic birds, this data pertains more to periods of growth and egg production and less to maintenance of adult birds. Our companion birds spend most of their time at maintenance, and during periods of reproduction, their investment in egg production is less than that of poultry, while their chicks' growth rate is faster. Welldesigned nutrition trials in Cockatiels, Budgerigars, and Zebra Finches can be used to predict when the "poultry" values are too high or too low. Using this approach, information has been collected for several critical dietary requirements, such as energy and lysine. Many of these trials have been conducted at UC Davis and have been published in the Exotic Bird Report and elsewhere over the years. In addition, several commercial diet manufacturers have used their own research facilities to further our knowledge of companion bird nutrition.
Unfortunately, there still are many gaps in our understanding, and a nutritionist must fill this void by applying general nutrition principles and information obtained in other avian species to the nutrition of the exotic bird. When attempts to further our knowledge are not based on sound nutritional principles, the results can be perilous. From the authors' point of view, many of the nutritional problems that are seen in captive birds result from anthropomorphism, romanticism and misinformation. Ascribing human characteristics to birds (anthropomorphism) can be dangerous, because the exact nutrients and the levels of each required by birds are considerably different than those required by humans. This is especially true during the critical periods of growth and reproduction. Differing digestive processes, metabolic capabilities and diseases of old age also distinguish birds from humans. Romanticism often takes the form of feeding birds what we think they would be eating in the wild. But companion birds are not wild; thus, their nutrient requirements are considerably different in their comfortable but sedentary captive environments.
Furthermore, rarely can we procure the exact food items that the birds eat in the wild; the domestic food items that are substituted are usually very different in nutritional content. Romanticism is sometimes expressed through avoidance of the ingredients found in poultry diets, especially corn, soybean meal and animal by-products. While poultry rations certainly have an inappropriate balance of nutrients for most of our exotic species, there is no compelling reason to completely avoid the ingredients used in poultry rations for diets fed to granivorous or omnivorous birds. Problems seen with these ingredients are due generally to contamination with molds or bacteria, but similar problems can plague every potential dietary ingredient if quality control is lax.
Misinformation is often an unfortunate consequence of unsubstantiated claims and advertisements made by a small subset of supplement and diet manufacturers. Health claims made for various elixirs, herbs and vitamin cocktails have rarely been documented or researched. While most are innocuous, some can cause nutrient toxicities or provide sufficient empty calories to diminish the nutrition provided by a complete diet. In general, to provide a companion bird with a well balanced diet, the owner must be aware of the general requirements for this type of animal. Ideally, the bird should be provided with a complete diet that meets its caloric and nutrient needs, and many commercially prepared diets do this.
Elizabeth Koutsos was a Ph.D. student worhing with Kirk Klasing on avian nutrition, including projects on vitamin A requirements and protein toxicity in Cockatiels. She received her B.S. degree from the University of Maryland and was an intern at the National Zoo in Washington, D.C.
