Meeting Amino Acid Requirements Increases Milk Protein and Milk Fat

In recent studies, increasing the supply of AA to meet the requirements for production increases milk protein and, to a greater extent, increases milk fat. Using recommendations for AA previously determined at Cornell University^5,6, the study⁷ shown in Table 1 assessed the effect of increasing the dietary inclusion of a rumen-protected methionine product to increase the methionine supply from 65 to 91 grams/day. Increasing methionine increased milk protein percent and yield, and increased milk fat by increasing de novo and mixed FA which are synthesized in the mammary gland. Meeting the requirements for AA can be achieved by feeding highly digestible NDF, starch, and sugar sources while balancing protein sources that are digested in the rumen (soybean meal, canola meal, hay crop silages) with protein sources that provide AA post-rumen (bloodmeal blends, heat-treated soybean meal, rumen-protected AA sources) to maximize microbial protein and reduce the excretion of protein nitrogen.