Changes in the bovine whey proteome during the early lactation period

To investigate time-dependent change in the bovine whey proteome during the early lactation period, a two-dimensional gel-based approach was used in this study. Milk samples were collected from five healthy Friesian-Holstein dairy cows up to 10 days postpartum. Spot patterns of whey proteins varied drastically from immediately after parturition to 48 h, but no significant changes occurred thereafter. Protein identification by mass spectrometry revealed that the ratios of caseins and immunoglobulins drastically decreased during 48 h postpartum, while those of lower molecular mass proteins such as alpha-lactalbumin and beta-lactoglobulin increased. More than 100 spots were detected, being much more abundant in colostral whey than in mature milk whey. Of a total of 25 proteins identified, four, viz. zinc-alpha-2-glycoprotein, vitamin D-binding protein, immunoglobulin G2 chain C and beta 2-microglobulin, were detectable only in colostrum. Our results indicate that most of the minor whey proteins in colostrum relate to the passive immunity of newborn calves, but some of them play significant roles in nutritional supplementation of the neonate. The characteristics of whey proteins in transition imply that enhancement of innate immunity becomes more important than protection of the neonate against pathogens via passive immunity after 48 h postpartum.