A review of methods for assessing the protein value of grain fed to ruminants

The protein value of feed grains for ruminant rations is currently described in modern feeding systems in terms of total protein, potentially degradable protein, and potentially undegradable protein. Progress is being made towards full standardisation of methods to measure these components, although it is a goal yet to be achieved. Whereas in the future it is desirable that protein value be defined in terms of individual amino acid availability at the intestine, in the immediate term it can best be described by the rate and extent of degradability of protein in the rumen and the availability in the intestine of the rumen undegraded protein. Refining the methodology for measuring these characteristics is important, but it is equally important that the existing methods be validated using in vivo experimentation.