FEED PROTEIN-FRACTIONS IN VARIOUS SOLVENTS OF RUMINANT FEEDSTUFFS

The classical protein fractions, ie albumins, globulins, prolamins, gl utelins and insoluble (or structural) proteins were evaluated in selec ted feedstuffs. Solvents used for classical protein fractionation were : dilute salt (1 M NaCl) in phosphate buffer (pH 7.0), aqueous alcohol (70% ethanol) and dilute alkali (0.05 M NaOH) with the subsequent sep aration of albumins and globulins by dialysis. In addition, crude prot ein content, soluble non-protein nitrogen, total true protein and solu ble true protein in McDougall's buffer from the same feedstuffs were d etermined. The soluble non-protein N contributed only a small portion of the total N in feedstuffs. Total true protein was approximately 8-1 0% for energy feeds, and then increased to 30% for plant protein sourc es, while the soluble true protein was about the same for energy feeds and plant protein sources. The major proportion of protein in plant p rotein sources was in the form of globulins, followed by albumins and lesser amounts of glutelins and prolamins. In contrast, the major prop ortion of protein in cereals was in the form of prolamins and glutelin s, followed by globulins and albumins.