Effects of Precision Essential Amino Acid Formulation on a Metabolizable EnergyBasis for Lactating Dairy Cows

摘要

Accurate description of both nutrient supply and requirements in the dairy cow continues to be a focus of ongoing research as we work to improve the efficiency of nutrient use in high producing cattle and reduce the environmental impact of milk production. In addition, producers feel the need to optimize their cattle's performance, improving profitability through feed cost savings while complying with nutrient management. As such, areas of opportunity exist in cattle nutrition that can accomplish these objectives, particularly involving protein feeds and nitrogen (N) metabolism. Current diet formulations rely on crude protein as the metric when evaluating N supply (NRC, 2001); however, the aggregation of all N containing nutrients into one metric creates variability in predicting supply, particularly when evaluating animal performance (Ipharraguerre & Clark, 2005). Considerable progress has been made in understanding lysine and methionine requirements of lactating cattle (Rulquin et al., 1993; Schwab, 1996), and providing recommendations and demonstrating improvements in performance when animals are properly supplied with these amino acids (Armentano et al., 1997; Noftsger & St-Pierre, 2003). The same efforts that went into the Met and Lys requirements and supply should be applied to other essential amino acids (EAA), calling for the abandonment of crude protein and the move towards a more accurate representation of N supply on an amino acid basis.