Biochemical and antibacterial properties of bovine mammary secretion during mammary involution and at parturition

Mammary secretions from four Holstein Friesian cows were collected during late lactation, early involution, and early in subsequent lactation. Changes of pH, concentration of serum albumin, immunoglobulin G, citrate, lactoferrin, and number of leukocytes in secretions were typical of milk from glands undergoing these physiological transitions. Whey prepared from a cow's secretions was evaluated for its capacity to inhibit growth of Escherichia coli, 60-Lilly, and a coliform strain isolated from mammary secretions of that cow. Wheys from different glands of the same cow differed markedly in their capacity to inhibit growth of coliforms. Inhibition of both strains by the wheys increased significantly during the dry period and was maximal in wheys collected day 15 of the dry period and at parturition in the subsequent lactation. The coliform strain isolated from a specific cow was inhibited more than Escherichia coli, 60-Lilly, by whey from the specific cow. Inhibition of the cow-specific coliform strain by the day 15 whey was reduced significantly after addition of ferric iron or sodium citrate. Addition of excess ferric iron or citrate to wheys collected at parturition did not alter significantly their inhibitory capacity within cow. However, reduction of growth inhibition was significant when data from the four cows were pooled.