A study of the composition of Clun Forest ewe's milk. IV. The proteins of ewe's milk and their variation with stage of lactation

Abstract

SUMMARYSix ewes were milked over a lactation period of 12 weeks beginning 2 weeks after parturition. Milk fat, total crude protein, and protein fractions were determined in each weekly milk sample.Milk fat and total crude protein in whole milk increased significantly over the lactation, attaining mean values of 5.8 and 5.9% respectively. The concentration of the caseins, total albumins and β-lactoglobulin in the whole milk also increased significantly over the lactation, with mean concentrations of 4.67, 0.80 and 0.54% respectively. The mean concentrations of these fractions, expressed as a percentage of the total crude protein, were, caseins 78.7, total albumins 13.5 and β-lactoglobulin 9.1.The following fractions, whose mean percentage concentrations in whole milk are given in parentheses, showed no significant trends over the lactation: α-lactalbumin + serum albumin (0.26), proteose-peptones (0.05), globulins (0.06) and non-protein nitrogen (0.35). Expressed as percentages of total crude protein, these concentrations are 4.4, 0.8, 1.1 and 5.6 respectively.The milk constituents synthesized in the mammary gland, i.e. fat, caseins and β-lactoglobulin showed significant correlations in concentration in whole milk as well as significant increases in concentration over the lactation.