51
Postpartum protein nutrition for dairy cows
Dietary recommendations regarding metabolizable protein (MP) and amino acid nutrition for dairy cows in the immediate postpartum period have not been completely defined. A state of negative protein balance present during this period, in which tissue amino acids are mobilized to support milk protein synthesis and gluconeogenesis, complicates estimates for supplying optimal amounts of metabolizable protein. Efforts made in attempting to formulate post-fresh diets utilizing MP methods, or estimating MP supplies from previous postpartum protein nutrition research diets, have demonstrated inconsistent responses when increasing MP amounts during the immediate postpartum period. Potential benefits when altering MP fractions to optimize transition to the lactation diet have not been explored. Previous research related to early-lactation protein feeding strategies suggests that offering greater concentrations or amounts of rumen-undegradable protein (RUP) may be beneficial to enhancement of production and health through meeting MP demands during periods of depressed dry matter intake (DMI) while lessening circulating plasma ammonia concentrations. However, the viability of this feeding strategy during the post-fresh period on maintaining health and ruminal adaptation to the lactation diet has not been evaluated. Research conducted by our group was developed to contribute to the pool of data supporting optimal MP feeding strategies for post-fresh dairy cows. Theoretical MP, microbial protein and RUP, contributions were altered between two research diets through selection of various protein ingredients to create a control diet and a higher RUP diet fed to cows during the postpartum segment of the transition period. Model-predicted total MP estimates utilizing post-study DMI values were similar between treatments, as were microbial and RUP estimates within the total MP supplied. Dietary rumen-degradable protein balance was significantly less for cows fed greater amounts of RUP. Results conclude that treatments had similar effects on means for DMI, milk production, and rumen fermentation end products; however, milk protein concentration was negatively affected for cows fed diets formulated with greater concentrations of RUP feed sources. Furthermore, after wk 4, animal performance from cows fed greater RUP tended to be adversely affected, suggesting that adequate rumen-degradable protein may not have been supplied to maximize rumen function. In addition, greater amounts of delivered RUP may have negatively affected DMI as intakes approached peak amounts.
Keywords: amino acid, postpartum, protein, transition cow