Quarter milk variation in immunoglobulins and ability to support phagocytosis

Milk samples were collected from two quarters in each of 8 cows that had Wisconsin Mastitis Test scores of less than 8.0. After letdown was stimulated, 35 ml of foremilk, the sixth 35 ml (middle milk), and 45 ml of strippings were collected by hand. Measured on each fraction were immunoglobulins, serum albumin, total protein, pH, percentage fat, Wisconsin Mastitis Test, and the ability of skim milk and whole milk to support phagocytosis of Staphylococcus aureus by isolated donor milk neutrophils. Foremilk and middle milk differed in immunoglobulin M (.014 to .018 mg/ml) and in the ability of whole milk to support phagocytosis (32 to 28% S. aureus phagocytosed). The following measures differed from middle milk to strippings: immunoglobulin A (.063 to .083 mg/ml); immunoglobulin G1 (.238 to .302 mg/ml); immunoglobulin M (.018 to .023 mg/ml); fat (3.9 to 7.4%); and Wisconsin Mastitis Test (5.0 to 9.2). Immunoglobulin G2, bovine serum albumin, total protein, pH, and the ability of skim milk and whole milk to support phagocytosis did not change. Although small differences may exist between foremilk and middle milk, foremilk gave reliable estimates.