Formulated Diets in Avian Nutrition

Introduction

Providing a bird with good nutrition often has different meanings for clinicians and clients. While the goal is to provide a diet that mimics the diet of that particular species in the wild, in captivity those strategies for feeding parrots are very different. For some of our clients, ignorance or culture may limit the bird’s food to table scraps or seed, while others feed a smorgasbord of food items that they prepare. Both tactics are considered to be unbalanced.

The general consensus of avian veterinarians is to provide a “balanced”diet, with recognition that nutritional requirements may vary between species of birds and for different life stages. There are few nutritional studies on the maintenance requirements for many of the individual species in the psittacine family, with many occupying a different ecological niche. Additionally, the role of a bird’s life stage on nutritional requirements is not well understood. Nutritional requirements will vary from a neonate, to a fledgling, to a mature adult, and finally to an aging bird.

One approach to provide a balanced diet is to offer formulated foods. There are several forms of formulated diets that may be considered “balanced.”

• Pellets
• Extruded diets that are commonly described as pellet-appearing foods
• Whole grains and/or seeds with pelleted material added to balance the entire product.

There are also some seed-based foods where a vitamin/mineral mix is coated on the outside of the seed that is often not hulled.

From a nutritional point of view, a bird eating any of the above diets, if they ingested the entire amount, would receive the needed nutrients. However, hulling of the seed by the avian patient results in the removal of vitamins and minerals needed for balance and more importantly for health. From a label perspective, a diet cannot claim that it is complete as there is no defined diet that is agreed upon as complete. The balance of a particular bird food is based on the manufacturer’s recommendation. Most of these balanced diets represent variations of a complete diet for galliforms or from a diet prepared according to the recommendations of the Association of Avian Veterinarians Nutrition Panel of Experts in 1996.

Pellets

True pellets are made by grinding a variety of grains based on the manufacturer’s recommendations, then adding vitamins, minerals and other components to make a final balanced product. The end product is nearly homogenous because of the small particle size afforded by the grinding process (Fig.1). The homogenous product makes it difficult or impossible for a bird to pick out and eat favorite parts and leave other parts behind. The homogenous food thus helps to ensure that the bird consumes a balanced diet.

To keep particles at the appropriate size, the ground mix is commonly put through a hammer mill. Liquids may be added, then the mix is pelleted by heating it to 70-80°C and moving it through holes using a roller. When the mix emerges as cylindrical particles of a constant diameter, a turning knife cuts the pellets as preset lengths. This is a non-cooked product where the components will have a longer fiber chain length but may not be as palatable as the extruded diet.

Extruded diets

Most of the “pellets” that are available today are really extruded diets. These diets are also made by mixing ground grains with vitamins, minerals and other components that will balance the final formula, but the “pellets” of an extruded diet are produced using higher temperatures and pressures. The ground mixture of grains, vitamins, and minerals is forced under pressure and temperature (between 90-180°C) through an extruder, which may involve a steam process using an injection technique. There may be a “dwell” time of anywhere from 30 seconds to several minutes. Moisture added as steam ranges between 0% and 20%. The food will take on the shape of the holes in the extruder plates. While water is largely maintained as a liquid in the pressurized extruder, the water is instantaneously evaporated when the mix leaves the extruder. Intracellular water is instantly evaporated, rupturing the plant cells. The food produced is partially hydrolyzed but the cooking can kill infectious agents if present.

 

 

Nutri-Berries and Avi-Cakes

Lafeber Nutri-Berries and Avi-Cakes utilize whole grains and seeds that are mixed with additional components to balance the product before it is stuck together. It is similar to a pellet nutritionally except that it is not ground (Fig. 2).

Seed-based foods

Some seed products put a pellet into the mixture to balance the entire product. This would require that the bird eat those pellets along with the seed to receive a balanced meal. Most often, birds do not eat the pellet in this type of product. Another variation is to coat the seed mix with vitamins and minerals to balance it. The coatings are often colored and are applied to the seed hull; however, the vitamin and mineral intake from the coatings is removed when the bird hulls the seeds.

 

Understanding formulated diets

It is important for veterinarians to understand the processes and the issues involved in avian nutrition to advise their clients appropriately to meet the individual needs of their patients. Each bird may have certain factors as well as medical conditions that need to be taken into account when advising owners on how to feed their birds. Avian veterinarians should be aware that most birds are fed seed with or without some table foods. It will take much discussion and owner understanding to get them to work on feeding diets that are more balanced. The goal of a balanced diet for the avian patient is to enhance their health and wellness. An additional goal is to use food as part of the bird’s enrichment. Enrichment enables each bird an expression of its natural behaviors for achieving a healthier lifestyle. It is hoped that the information provided will help in discussing these issues with your avian clients.

References