Relationship of Blood Serum Protein and Protein Fractions to Milk Constituents and Temperature-Season

Blood serum protein and protein fractions were determined in 265 samples from 62 lactating Holstein cows over one calendar year. Temperature-seasonal changes (cool, optimum, hot) were responsible for significant linear and quadratic fluctuation in serum protein fractions. Serum albumin, β-globulin, α2- globulin, and the A:G ratio significantly decreased as seasons progressed from cool to hot. Further, globulin and γ-globulin both increased significantly from cool to hot seasons. An a1bumin:globulin ratio (.56:1) was inverted. Milk fat percentage was positively correlated with serum albumin percentage and a1bumin:globulin ratio and negatively correlated with total serum protein, and serum globulin and γ-globulin percentages. No correlations were significant between Wisconsin Mastitis Test or Direct Microscopic Somatic Cell Count and any of the serum protein constituents or total serum protein. Monthly 4% fat-corrected milk was negatively correlated with total serum protein and serum globulin percentage and positively correlated with serum α2-globulin percentage. © 1972, American Dairy Science Association. All rights reserved.