ARTICLE 68 FEED & ADDITIVE MAGAZINE October 2025 Lysine and methionine are the first two limiting amino acids in dairy cow diets and hence limit performance. For many years there has been a focus on supplemental methionine which is usually the first limiting amino acid for milk protein yield. The opportunity and awareness of lysine has increased in recent years for a number of reasons, such as the capacity to increase milk yield, focus on lower protein diets, lower soya diets in some parts of the world, and because of the pressure for improved sustainability and lower nitrogen diets. Balancing for amino acids, specifically lysine and methionine, can allow for decreased protein in the ration and potential to improve efficiency of nitrogen use in the cow. LYSINE IN THE MAMMARY GLAND Although methionine has been extensively studied for its capability to reliably increase milk protein content, the response to lysine is less well understood. This may be because lysine and methionine have very different roles within the dairy cow. Lysine is taken up in excess of requirements for milk protein synthesis in the mammary gland whereas the mammary gland only takes up as much methionine as needed for milk protein synthesis. This allows lysine to be broken down and supplement the formation of nonessential amino acids if any are lacking. It can also spare other essential amino acids that behave similarly in the mammary gland, such as branched-chain amino acids (leucine and isoleucine specifically). This difference in how the cow uses these two amino acids may explain why the response to lysine is more variable. A DEEPER LOOK INTO LYSINE In an attempt to better understand the response dairy cows have to increased metabolizable lysine, Arshad et al. (2023) conducted a meta-analysis of 13 research studies feeding rumen-protected lysine (RPL). They wanted to understand how varying levels of metabolizable lysine impact production in dairy cows and potentially identify an optimal level of lysine. One important takeaway from this meta-analysis is that timing and duration of feeding supplemenThe interaction between lysine and methionine in increasing milk fat and feed efficiency is a perfect example of why balancing for all essential amino acids is so important. In an ideal world, we could provide exactly the required amount of essential amino acids, but this is difficult with only rumen protected forms of lysine and methionine currently available in the market. In this case, if we only balance for lysine or methionine instead of both, we could be missing out on milk fat and making the cows less efficient. TURBO CHARGING DIETS WITH INCREASED DIETARY LYSINE Dr. Laura Niehues Technical Services Specialist Balchem Animal Nutrition & Health
RkJQdWJsaXNoZXIy MTUxNjkxNQ==