For many years dairymen and their nutritionists have discussed six primary things concerning their lactating dairy diets; protein, energy, fiber, vitamins and minerals… and water. In this article, we’ll discuss amino acids and what they mean to a lactating dairy cow. With the high price of feed, especially protein, dairymen need to make sure that they are feeding the proper amounts of protein or amino acids to maximize production and income over feed cost (IOFC).

Advances in technology allow us to balance diets for more specific nutrients, including amino acids instead of simply looking at crude protein (CP) of the diet. In many cases when balancing for specific amino acids, CP could be reduced, which may lower feed costs, and potentially maintain or even increase production. Amino acids are generally defined as the building blocks of protein, which we all know is very important for milk production, reproduction, immune function, growth, etc. Basically, the cow breaks protein down into amino acids. There are many amino acids that make up protein such as lysine, methionine, arginine, threonine and leucine to name a few. There are many more! Some amino acids can be synthesized in the cow’s digestive system while others can’t. Amino acids that are not synthesized are called “limiting amino acids” and must be supplemented in the ration. Generally speaking, from a milk production perspective, the two most limiting amino acids are lysine and methionine, which when delivered at the optimum levels allow the cow to use more of the dietary protein for all necessary functions, such as milk production. Ok, so what are the optimum levels? Research is still ongoing but as a general rule, minimum concentration of lysine should be approximately 6.65% and methionine around 2.2% of metabolizable protein, which is the amount of protein that the cow actually breaks down and utilizes for production, growth and/or other bodily functions. Some research has shown production responses to lysine as high as 7.10% and methionine as high as 2.33% of metabolizable protein. While these are optimum levels and sometimes hard to reach, maintaining an approximate 3:1 ratio of lysine to methionine in the diet is thought to be optimal. Protein that passes out of the rumen or “by-pass protein” is digested to amino acids and mostly absorbed from the lower digestive tract. After absorption, the amino acids are released into the blood where they are available for tissues to utilize for maintenance and productive purposes. Since the rumen can degrade amino acid, these limiting amino acids must be able to pass through the rumen to aid the cow. There are encapsulated amino acids, that are commercially available, to help your nutritionist attain these levels in your diet.

Today’s dairy cow is under enormous pressure, along with her owner, to perform at a high level! We’ve known about amino acids for a long time, but not until recently have we been able to balance dairy diets to maximize amino acid technology and lower crude protein levels in the diet. It’s a new way of thinking for many dairy nutritionists! But rather than looking at the crude protein of the diet, we need to be focusing on amino acids and what the cow really needs.

Talk to your Augusta Co-op dairy specialist about balancing for amino acids!

Denny Sells, H.J. Baker & Bro., LLC.


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