beta-Lactoglobulin and alpha-lactalbumin in mammary secretions during the dry period: parallelism of concentration changes.

Proteins in mammary secretions were examined during the dry period of four cows. Polyacrylamide gel electrophoresis was used to determine relative changes in the electrophoretic profiles of whey proteins in the mammary secretions. Concentrations of beta-lactoglobulin and alpha-lactalbumin in dry cow secretions were determined by immunoassay. Concentrations of both proteins changed in parallel during the dry period. Concentrations of beta-lactoglobulin and alpha-lactalbumin decreased during the first 30 d of the dry period but generally remained above .1 mg/ml secretion. A transient increase in beta-lactoglobulin and alpha-lactalbumin concentrations occurred at about 40 d after drying-off, prior to the prepartum increase.