This report reviews the energy and protein requirement systems for dairy cows
currently used in Britain and presents a new approach, along with the outline of
a model for its implementation. Current systems give little consideration to the
responses of the animal to changes in the nutrient supply, or to interactions
between dietary constituents in their effects on digestion and metabolism.
Neither do they predict any effect on the partition of nutrient use between milk
and body, or changes in the yields of milk fat, protein and lactose, which
determine the commercial value of the milk. Therefore the systems, although not
inaccurate, lack relevance to the current