By: Robert Bailey
President and Dairy Nutritionist

Protein is made up of building blocks called amino acids. The body can synthesize many amino acids which are called nonessential amino acids. If the body cannot synthesize sufficient amounts of an amino acid to carry out necessary physiological functions, it is called an essential amino acid. This definition generally applies to nonruminants, as ruminants have the ability to synthesize all amino acids. It is important to understand that ruminants still require amino acids. The question that research has been dealing with is what amounts of which specific amino acids are needed to support higher and higher production in dairy cattle.

Research has shown that for higher producing cows, a desirable level of %UIP/CP can vary from 35- 40%. At ANC we strive for levels of 36-39%. It is important to understand that UIP is dependent on amino acid analysis of diet feedstuffs. For example, it is possible to have the proper %UIP, but if the ration is short a limiting amino acid, production benefits will not be realized. Conversely, if all necessary amino acids are present but not in a bypass form where they can get to the small intestine the added benefits will not be seen.

Because lysine is readily available through various protein sources in a bypass form, a ration analyst can usually balance a high production ration for lysine, especially when soybean products are available. Rations very high in DIP, such as diets comprised mainly of high protein hay and haylage, become difficult to economically balance for amino acids, due to the lower supplemental protein requirement. This is part of the reason ANC advocates that such feeds need to be diluted with corn silage or other lower protein feedstuffs.

We have also been conducting feeding experiments utilizing supplemental protected methionine for about six months. Evidently we have done "too good" of a job with our ration program, because response is minimal at this point. The cost of the added methionine will only cash flow into a profit if the ration is quite short of methionine, say 20-30 grams. We haven't encountered this yet, but have come up with rations being 5-10 grams short, according to some research recommended levels. However, even requirement levels are not known for certain.

My theory is that the rest of the ration has a lot to do with how efficient a cow synthesizes methionine. At ANC, we pay particular attention to how we balance for Non-Fiber Carbohydrates (NFC), ADF, NDF, and NDFe. Keeping these factors in check creates a better environment for rumen microflora. This allows the cow to more easily synthesize limiting amino acids from available nitrogen in the rumen, which in turn, reduces the amount of supplemental lysine and methionine needed.

Methionine in a form that can be purchased is quite expensive at this point. Although we have not seen an increase in milk protein percent, or total protein pounds, we will continue our methionine field studies. Many thanks to Degussa Corporation for helping us with amino acid balancing, suppling methionine, and providing us with thousands of feed analysis to update our feed files! Currently, their Mepron product seems to be the best buy.