We know balancing for amino acids – ensuring the amount of amino acids supplied meets the needs of the dairy cow – can have beneficial effects for dairy cows and the overall dairy operation. The question is, How do we achieve that balance?
Through recent research, we can now predict the amino acids that are needed for both maintenance and milk protein production. We can also predict the amino acid profile of microbial protein and rumen undegraded protein (RUP) from feed ingredients. Matching these sources of amino acids with the amino acid requirements is the key to amino acid balancing.
When one or more amino acids is in excess of the amount needed, then that excess amino acid is wasted. Similarly, when one or more amino acids is limiting, the remaining amino acids cannot be used for protein synthesis.
This was well illustrated by the organic chemist Justus von Liebig. Von Liebig demonstrated that production is regulated by the scarcest resource. A barrel will only hold as much water as the shortest stave, and the longer remaining staves do not permit more water to be added. The additional length is, in effect, wasted (see figure).
The best balance occurs when all essential amino acids are near requirements, none is limiting, and none is excessive.