FEED PROTEIN-FRACTIONS - RELATIONSHIP TO NITROGEN SOLUBILITY AND DEGRADABILITY

The classical protein fractions (albumins, globulins, prolamines, glutelins), and N soluble in 10% Burroughs mineral mixture were measured in 43 feeds. Solvents used for classical protein fractionation were: water (distilled deionized), dilute salt (.5% NaCl), aqueous alcohol (80% ethanol), and dilute alkali (.2% NaOH). Correlations between the fractions of protein extracted by each solvent and N soluble in Burroughs mixture were: water, .58; dilute salt, .50; aqueous ethanol, –.11 dilute alkali, .17. The combined fractions of protein extracted by water and dilute salt was highly correlated (.82) with N solubility. Selected feeds were evaluated using in vitro and in situ polyester bag systems. Nitrogen disappearance from bags in vitro at 15 min and 12 h was correlated with N solubility (.66 and .54, respectively). © 1990, American Dairy Science Association. All rights reserved.