MILK WHEY PROTEINS IN PLASMA OF SOWS - VARIATION WITH PHYSIOLOGICAL-STATE

The whey proteins alpha-lactalbumin and beta-lactoglobulin have been i nvestigated as potential markers of mammary development in sows by mea suring their concentrations in plasma. The whey proteins were isolated from porcine milk by gel filtration, ion-exchange and hydrophobic int eraction chromatography, characterized by several criteria and used to raise antibodies. Specific radioimmunoassays were set up for porcine alpha-lactalbumin and beta-lactoglobulin and validated for use in porc ine blood and milk. Plasma levels of the whey proteins were measured i n sows that were pregnant, suckling litters post partum, weaned abrupt ly at birth or were pregnant but mastectomized. Both whey proteins sho wed similar patterns in plasma post partum, falling from a maximum 1 d after parturition to values < 0.02 % those in milk by day 4-5 post pa rtum in suckling sows and showing a transient peak associated with ear ly involution before declining to very low concentrations in non-suckl ing sows. alpha-lactalbumin was first detected in the last week prepar tum, rising markedly in the 3 d before parturition, correlated with ri sing prolactin (r = 0.988) and falling progesterone (r = -0.998). beta -Lactoglobulin rose much earlier from 5 weeks prepartum, at the time w hen lobulo-alveolar mammary development is occurring, and correlated ( r = 0.929) with oestradiol-17 beta. In mastectomized sows, concentrati ons of whey proteins in plasma were reduced by 90% or more when compar ed with intact animals, though following a similar pattern. This study shows that whey protein concentrations in plasma vary with physiologi cal state and reflect aspects of the development of the mammary gland. The very different profiles for alpha-lactalbumin and beta-lactoglobu lin prepartum indicate that they are differently controlled.