112 Young Scholar Presentation: Protein and Amino Acid Nutrition in Fresh Cows

Abstract

During the 4 weeks after parturition, postpartum dairy cows (i.e., fresh cows) have the highest risk of disease and metabolic disorders. This is largely because nutrient requirements for lactation outweigh the cow’s metabolizable intake. As a result, cows enter negative nutrient balances and mobilize endogenous protein and energy stores to meet demands. Although negative energy balance, in terms of mass, is more negative than protein balances over this time frame, intake of metabolize protein (MP) and its amino acid (AA) profile may influence the performance and health of fresh cows more than increasing energy intake. Better performance from greater MP and AA supplies may also carry over and enhance milk production further into lactation. In our recent experiment, increasing MP supplies to fresh cows by feeding a greater rumen undegradable protein concentration (RUP; 7 vs 10% of DM) also increased milk and milk component yields. However, when the AA profile of the supplemental RUP was optimized to mimic the AA profile of casein, the greater yields were sustained much further into lactation. This may be because fresh cows fed the “casein like AA profile” had improved health and less body protein catabolism than cows fed a similar MP concentration. However, production responses with a greater MP intake depended on what the RUP replaced in the diet and on parity. When replacing forage fiber with RUP instead of nonforage fiber, multiparous cows had a reduction in milk and milk fat yields whereas primiparous cows performed similarly regardless of what type fiber was replaced. This suggested reducing forage fiber in a high MP diet will not increase overall MP intake, and multiparous cows may require more forage fiber during the fresh period than primiparous cows. Overall, MP intake and the AA supply is important for the health and production of fresh cows.