Changes in the quantity and composition of mammary gland secretion in the dry period between lactations: I. The beginning of the dry period

Abstract

SummaryThe changes in the yield and composition of the mammary gland secretion in the first 16 days of the dry period have been investigated in 6 cows. The quantity of secretion, lactose, potassium, casein, α-lactalbumin, β-lactoglobulin and fat present in the gland decreased rapidly. A decrease was also observed for sodium, chloride, residual albumin and proteose-peptone + globulin but was much less marked. Changes in composition were qualitatively similar to those normally occurring at the end of lactation but they were much more pronounced. Within 8 days after drying-off the concentrations in the secretion of sodium, chloride and potassium were similar to those of blood. There were differences between, animals in the rate at which the changes developed. As the secretory activity of the gland ceased, the constituents of the mammary gland secretion appeared to be resorbed.