Roles and mechanisms of methionine on milk productivity of dairy cows

Abstract. The dairy industry has been an important part of the world's food industry. There are many factors affecting the milk production performance of cows, among which the nutritional factors are very important. Methionine has been found to have a critical role. Supplementation of methionine in a lactating diet can improve the lactating performance of dairy cows. Methionine, as one of the limiting amino acids (AA), enhances the biosynthesis of proteins in breast cells. Methionine can affect AA transportation by regulating the mTOR signaling pathway and regulating gene expression, such as the SLC1A5 gene (encoding ASCT2). Furthermore, methionine can also be used to synthesize glutathione (GSH) to improve the antioxidant capacity. Supplementation of rumen methionine showed immunity-enhancing effects. This review summarizes the effects of different forms of methionine supplementation on the performance of lactating dairy cows, including rumen methionine, N-acetyl-l-methionine (NALM), and coated methionine. This review discusses the role of methionine in dairy cow nutrition and the approaches of methionine supplements to improve lactation performance, aiming to provide an explanation for nutrient regulation in dairy cow feeding, in order to improve dairy cow productivity. Future research is required to better elucidate the methionine-associated metabolic changes during lactylation, as well as practical to optimize the approaches to improve dairy production.