Monday, November 01, 2010

Methionine in chook food

The absence of feathers on hens can be caused by several things and can be separated into two groups: 1) birds that don't grow feathers and 2) birds that pull them out or break them off. Either problem can be managed by correcting the cause.

The most common reason that feathers do not develop is a deficiency of a critical amino acid (methionine) from the diet of the birds. The feathers of birds contain high levels of methionine which is one of only a few amino acids that contain sulfur, an essential component of feathers. An adequate level of methionine is required in the diet. It occur naturally in many grains but a deficiency results in reduced growth and feather development. A methionine deficient bird will tend to eat feathers in an attempt to satisfy a craving for this amino acid. A bird may even pull them from its own body or from other birds.

Feed rations that are high in plant proteins, such as soybean meal, will contain natural levels of amino acids, including methionine - eliminating the need to add supplements to the ration. But take care not to raise protein levels too much as high-protein diets are not healthy for poultry or the environment. If the hens really have access to pasture (which often has a protein content of 30%) it can be counter-productive to feed a supplementary ration with a protein level of more than 17 - 18%.

Methionine is used extensively as a dietary supplement by human body builders (to enhance muscle bulk). And is is one of the major reasons that commercial meat poultry growers are able to grow their birds so quickly that they are ready for slaughter in just six weeks.

For egg production, if the grains used in making poultry rations contain inadequate levels of methionine, some suppliers add synthetic methionine (DL methionine) to the dietary mix to ensure that the birds receive sufficient amounts. All quality poultry feeds are formulated to contain adequate methionine to maintain growth and feather development. However, if additional grains (such as corn) are fed with the complete feed, then the amount of methionine consumed by the bird can be inadequate for their development. Feeding of additional grains with complete poultry feeds is not recommended.

Chooks that grow feathers well, but which are later pulled out or broken off, the cause is usually management related.

If methionine is added to poultry feed, egg producers should ensure that it is the natural version and not the synthetic DL methionine which is widely available (and cheaper).  Laying hens that consume 100 g of feed per day should ideally have 0.30% methionine in their diet - not hard to achieve with a properly balanced grain-based mix.

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