Sector Poultry

The foundational principles of protein in the poultry diet

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Proteins are essential for life. Human and animal bodies consist of trillions of cells, and every one of them contains protein. Unfortunately, in the body, most of these proteins have a life span of only two days or less, so dietary protein is needed for a steady supply of amino acids, the building blocks of protein.

What are proteins?

Proteins are essential building blocks to all cells and play a predominant role in healing, carrying oxygen, protecting against diseases, providing energy, and (of course) building muscle. Proteins are large molecules made up of hundreds of amino acids bound into long chains with peptide bonds. There are 20 different types of amino acids that can be combined to make a protein, the number and sequence of these amino acids are unique to each protein and determine its shape. The shape of the protein determines its function, for instance, as a muscle or enzyme. A good summary is the alphabet, the amino acids are ‘letters’ that can be arranged in different ways to create ‘words’ (peptides) and an entire protein is a ‘language’.

Some amino acids can be synthesized by the body from other molecules (mainly glucose and amino groups), and are often referred to as non-essential amino acids. Other amino acids cannot be synthesized and must be supplied by the feed. These are called essential amino acids, for instance, lysine and methionine. As amino acids are used for different processes, the requirements differ per amino acid, species, and life stage.

Enzymes are proteins whose function is to assist in the breakdown of dietary proteins. Though there are many enzymes involved in protein digestion, the most important one to know is protease. In the small intestine, protease breakdown feed proteins into short chains of peptides. From here, another enzyme (peptidase) loosens the peptide bonds and thereby separates the amino acids.

Figure 1: Breakdown of protein by protease and peptidase

Excessive protein

Although dietary protein is of high importance, too much protein also has disadvantages. First, protein is expensive, so undigested protein is a waste of money. Next to that, a protein that is not digested and absorbed in the small intestines will make its way to the hindgut. In the hindgut, undigested protein is fermented by bacteria that then release ammonia. Ammonia damages the gut wall, reducing the colon’s ability to absorb water. As a consequence, the feces will become wetter and contain higher ammonia levels. The presence of both water and ammonia increases the incidence of footpad dermatitis in poultry. Also, the ammonia levels in the air will increase, which can harm the respiratory system.

Additionally, hindgut fermentation often aids in the presence of unwanted bacteria, like those in the Clostridium genus. This bacteria can overgrow on an undigested protein supply and lead to an unfavorable shift in the gut microbiome. If the overgrowth is too excessive, these (and other) pathogens can lead to inflammation in the gut and eventually a leaky gut.

Reducing protein levels

As excessive protein increases wet litter and the incidence of footpad lesions, reducing crude protein levels in the diet can improve both footpad health and bird welfare. When lowering dietary protein levels, ensure the flock is still receiving suffi­cient levels of all essential amino acids.

As mentioned before, several amino acids are needed to synthesize protein and the amino acid requirement of each protein is different. When the appropriate amount of an amino acid is not available, it is the first limiting factor that deter­mines the growth of the bird. An easy visualization is Liebig’s barrel, in the picture below, methionine is the limiting amino acid (Figure 2). Nowadays, there are synthetic amino acids that can help fulfill the need for amino acids while reducing dietary protein levels. If methionine is the limiting amino acid we can add synthetic methionine until it is not the limiting factor anymore.

Next, as it is the next limiting factor, lysine will need to be added to further increase the water level in the barrel. There­fore, to achieve a balanced protein profile, both lysine and methionine need to be added. In this way, similar levels of growth perfor­mance and quality can be achieved with lower crude protein levels.

Figure 2: Liebig’s barrel shows how the first limiting amino acid determines the growth of the bird

Dietary protein vs. digestible amino acids

Protein intake is crucial for a lot of metabolic processes: the immune system, the digestive system, and for building muscle. The key to successful protein management is sup­plying poultry with adequate levels of protein. To not cause problems, it is important to know the exact demand of the bird at the time of feeding (based on breed, age, environment, etc.). Not to be forgotten, is the quality of the components used in the feed. Depending on the digestibility of the ingre­dients selected, not all of the protein in the product will be made available to the animal (Figure 3). This is why knowing the exact nutritional values of the macro-ingredients can help provide better feed.

The exactness of protein formulation

Figure 3: Depending on the quality of the source, the amount of crude protein will be different from the actual digestible amino acids made available to the animal. By formulating on digestible amino acid ratios, you formulate on what is really used by the birds while also taking into account the difference in requirement per amino acid.

Feeding the right amount of protein to poultry is crucial for optimal growth, health, and welfare. Proteins are the building blocks of life, essential for a wide range of metabolic process­es, including building muscle, supporting the immune system, and aiding digestion. However, excessive protein can be wasteful and even harmful to bird health, leading to wet litter, footpad lesions, and gut inflammation. Therefore, reducing protein levels while ensuring all essential amino acids are still supplied can improve overall bird health and welfare. With careful attention to protein management and feed compo­sition, it is possible to maximize production potential while minimizing the risk of diseases.

Your Earlyfeed expert
Stefan Alius
Product Manager Poultry

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