FUNDAMENTALS OF AVIAN NUTRITION - WHAT IS PROTEIN QUALITY?

This my second article on protein and is about defining the importance protein quality and establishing the balanced protein requirements of birds.

The capacity of the bird to use dietary protein as a source of amino acids and nitrogen is influenced by the digestibility and the quality of protein presented to the bird from the diet.

THE THEORY OF AMINO ACID BALANCE

What is meant by protein quality? A good quality dietary protein is one that can provide the bird with all the essential amino acids in the correct relative quantities to meet the bird’s daily requirement for essential amino acids and nitrogen. No single feed ingredient can supply all the essential amino acids required by the bird in the correct quantities. Combining various feed ingredient protein sources is required to meet the bird’s daily requirements.  Also, the use of single amino acids is required to ensure an proper amino acid balance is achieved without overloading the diet with excessive amount of nitrogen and non- essential amino acids. The physiological state of the birds will also determine its amino acid requirements. For example, birds at maintenance (tissue replacement and/or repair and feather turnover) will require different amino acid requirements to breeding birds or different for young growing birds that are growing rapidly. The value of a particular ingredient will depend on the physiological state of the bird being fed and its ability to meet the type and level of amino acids required by the bird.

A simple illustration is shown in Figure 1 A-D.

 Figure 1-A. Consider a barrel of water as representing the total amount of balanced protein that is required by the bird daily to meet its overall protein needs. This is different depending on the physiological status of the bird. For growing birds, the demand will be higher than for birds at maintenance. Consider the barrel is made up of various staves of different thickness and height each stave representing the type and amount of a single amino acid in the protein required by the bird. The amount of water we can put into the barrel is limited and represented by the shortest stave in the barrel. This represents the limiting amino acid. The staves above the water level have no function and therefore represent amino acids that are wasted and must be excreted by the bird. In nutritional terms this represents excess amino acids. Since amino acids cannot be stored the body has to remove them. The nitrogen portion of the amino acid is excreted in the urine as uric acid (after meeting the minimum requirement for nitrogen) and the carbon skeleton left goes into fat metabolism and stored as fat. This is an energy cost to the bird and can also result in obesity if the protein is too imbalanced.

Figure 1-B. If we can fill the gaps, this will allow more water to be added to the barrel and the amount of waste above the water line is now reduced. This represents an improved utilisation of the amino acid present in the diet and less amino acids being wasted. We can use other protein sources or individual amino acids to fill the gaps in protein being fed to the birds.

Figure 1-C. As we continue to fill the gaps, we can add more water. As we add additional amino acids to the diet, we continue to balance the protein and reduce the amino acid waste with less cost to the bird. This means more protein (in form of body tissue, feather, or egg protein) is being made since we can utilise the amino acids that would be otherwise be wasted in an unbalanced diet.

Figure 1-D. Finally, we keep filling the gaps until we can now fill the barrel to the top. We continue add amino acids until the protein in the diet is completely balanced. Choosing the correct type of proteins and amino acids that help to fill the gaps in protein delivered by our main ingredients, i.e., seeds and grains, improves the efficiency and utilisation of the seed by the bird and improves the nutrients available for maintenance, growth, and feather quality.

Our TummyRite™ Range of products, as a protein balancer, as one of their many functions, provides the essential amino acids to plug those gaps in protein provided by the seeds.

Our complete softfood products, Prosperity™ and StartRite™, have been scientifically formulated to meet the daily amino acid requirements of young birds in their early stages of life and development.

ESTABLISHING DAILY AMINO ACID REQUIREMENTS OF PASSERINE AND PSITTACINE BIRDS

The feeding of birds in a captive environment is about maintenance, growth, health, and reproduction. Malnutrition (underfeeding and overfeeding) is one of the most common health issues found in captive birds. The feeding of captive birds is still more of an art, based on experience and trial and error (experimentation) rather than an exact science. There is much published in books and articles about feeding birds but very little on whether these feeding practices do meet the daily nutrient (protein and amino acid) requirements of the specific bird species and their physiological status at the time. This is not to denigrate the value and experience and experimentation of dedicated breeders have made over many years, but to avoid nutrient deficiencies, and increasingly more important, over feeding and nutrient excesses we need to progress further and to be able to quantify the amino acid requirements of each bird species at various stages of their life cycle and physiological status. This means determining the actual amount of the amino acids that an individual bird must consume to meet its daily requirements at their physiological stage of development and to structure the dietary components in such a way to ensure this actually happens in practice. Good nutrition is about nutrient delivery to the bird daily in the correct amount and in the correct balance at the right time according to their physiological status.

 In my next article I will discuss how do we deliver the correct amount of balanced protein to birds daily.


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