Metabolizable Protein and Amino Acid Nutrition of the Cow:

Considerable progress has been made over the last 30 years in the United States to develop systems that describe protein requirements and protein adequacy of diets for dairy cows. Ration formulation systems have moved from balancing diets for crude protein (CP) and digestible protein to the use of nutritional models (e.g., NRC, 2001; CNCPS, CPM-Dairy, and Amino Cow) that recognize that the cow has two sets of dietary protein requirements (RDP and RUP) and that metabolically, she has requirements for individual amino acids (AA) rather than metabolizable protein (MP) per se. While current models and feed inputs are less than perfect, and our understanding of the N requirements of rumen bacteria and the AA requirements of the cow at different physiological states and levels of milk production are not clearly defined, current knowledge and consistent use of a model allows for more precise formulation of diets for RDP, RUP and AA.