Amino acid balance in the lactating dairy cow ration is essential for optimal nutrient metabolism, strong immunity and milk synthesis. When the ratios of amino acids in the diet most accurately reflect the cow’s needs, she becomes most efficient at metabolizing all dietary energy sources, therefore increasing efficiency at producing milk and components. This allows for remaining energy to be shuttled to greater production, immunity, and other metabolic processes. Providing essential amino acids in a diet helps us steer clear from deficiencies that may cause decreased growth and production, decreased nitrogen balance, reproduction issues, immunosuppression, anemia, and decreased liver health and efficiency.
Methionine is a limiting and essential, amino acid important to many metabolic processes, particularly those involved in liver metabolism of nutrients, immune function, and milk synthesis. Methionine does not just drive milk and protein synthesis, but is also instrumental in the formation of the non-essential amino acid cysteine. Cysteine is necessary for milk protein synthesis and a major precursor for immune system antioxidants. However, when methionine is lacking, cysteine synthesis suffers, and the cow begins to show signs of oxidative stress, inflammation and immunosuppression.
Transition cows are at highest risk for developing a methionine deficiency. Steep acceleration of milk yield, decreases in dry matter intake, and heavy demand for methionine in the liver, immune system, and mammary often create a negative methionine balance in the transition animal. When methionine is deficient in a transition or lactating cow diet, the liver becomes less productive at metabolizing dietary proteins, fats, and carbohydrates, causing energy to be lost while the animal tries to make up for the deficit in less efficient ways (often pulling proteins and glycogen from muscle). As milk yields rise, the deficiency causes decreased protein and fat composition. The immune system also suffers without enough methionine to produce antioxidant and immune system precursors such as cysteine. This creates a losing battle in a highly stressed, high producing animal.
Supplementing and balancing the diet with a bioavailable, rumen-protected methionine product can help to alleviate methionine deficiency during high production and stress. Supplemental methionine in a diet enhances liver metabolism of dietary energy sources, causing stimulated secretion of very low density lipoproteins (VLDL’s). In turn, VLDL’s can be used as an efficient source of energy to the cow while the incidence of fatty liver and blood NEFA decreases. The decrease in NEFA will typically cause an increase in dry matter intake, creating a positive cycle during the stress times, particularly transition. Of equal consideration is the positive effect supplemental methionine has on the immune system, being a key component in the relief of oxidative stress and inflammation. When this whole package is put together, supplying a quality, bypass methionine during transition increases dry matter intake, increases liver efficiency and metabolism, and bolsters the immune system, leaving remaining methionine and energy for the important task of fluid milk and protein production.