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The language of nutrition: EAA (Essential amino acids)

Jessica Tekippe Published on 11 March 2015

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In layman’s terms,what does EAA mean?

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Essential amino acids (EAAs) are the amino acids that need to be supplemented in the dairy diet. Dairy cows cannot synthesize enough of these amino acids to maintain their body functions at peak levels.

In comparison, non-essential amino acids (non-EAAs) are made in sufficient quantities by the dairy cow to meet her needs and do not require supplementation.

EAAs and non-EAAs serve as the building blocks of proteins. Together they equal the total amount of protein in the ration. The EAAs can be supplied in three ways: natural feed ingredients, synthesized feed nutrients (rumen-protected) or rumen microbes.

Of the 10 essential amino acids for dairy cattle, two are first-limiting. That means that they typically are the first two to become deficient in dairy diets. That’s important, as a deficiency can literally limit or put a ceiling on dairy production and performance.

The first two limiting EAAs are methionine and lysine. To help meet their requirements, rumen-protected methionine products have been offered for some 20 years. Rumen-protected lysine products began being marketed approximately seven years ago.

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Balancing rations for amino acids means assuring that the ration contains sufficient quantities of the first two limiting amino acids, i.e., methionine and lysine. This can be done more easily than ever before using today’s ration formulation software.

Rumen-protected products for methionine and lysine are readily available to deliver the precise quantity of the EAA required to meet ration requirements.

As a result of amino acid balancing, lower protein levels typically are fed. Rations with 14 to 16 percent protein are increasingly common. Rumen protection allows the essential amino acid to escape the rumen for absorption in the small intestine.

Feeding lower protein levels typically reduces the cost of the ration and decreases nitrogen excretion. In addition, herd performance typically improves. Overfeeding EAAs, on the other hand, unnecessarily increases the ration cost and creates an extra energy expenditure for the cow. She now must convert surplus amino acid to urea for excretion.

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How is EAA measured?

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Each EAA is measured in grams, as dairy cattle require an absolute amount of each EAA. For that reason, EAAs typically are not given as a percent of the ration’s protein content.

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What impact does EAA haveon a ration?

Protein production in the cow can be compared, big picture, to putting together a large puzzle. Each piece has a specific place where it fits and a certain order in which it is to be placed in the puzzle.

If a cow is missing or short one of the EAAs, no matter how hard she tries, she cannot complete the puzzle. If she is missing a non-EAA, all she needs to do is rearrange the chemical configuration of another amino acid to form the one she needs.

In this case, the puzzle at the dairy level takes the form of milk production, growing a calf or developing muscle. This is why it is important to make sure the EAAs are at the required levels.

Historically, nutritionists and producers viewed the protein part of a diet in terms of crude protein. Next, they viewed protein as metabolizable protein. Today, they increasingly speak of protein in terms of specific amino acids. Virtually all nutritionists are interested in amino acid balancing.

Nutritionists and producers are encouraged to go one step beyond recognizing the need by dairy cows for EAAs to balancing for the most limiting amino acids. Doing so ensures that their herds will more fully reach their full potential. PD

Jessica Tekippe
Ajinomoto Heartland, Inc.

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