Bovine immunoglobulin G, beta-lactoglobulin, alpha-lactalbumin and serum albumin in colostrum and milk during the early post partum period

Colostrum and milk samples from 60 Holstein-Friesian cows were analysed for concentrations and yields of immunoglobulin G (IgG), P-lactoglobulin (beta -lg), alpha-lactalbumin (alpha-la) and serum albumin (BSA) throughout the f irst 16 milkings post partum (8 d of lactation) using a single radial immun odiffusion assay. Concentrations (mg/ml, means+/-SD) at first milking were IgG 59.8+28.5, beta-lg 14.3 +/- 4.6 alpha-la 2.04 +/- 0.6 BSA 1.21 +/- 0.44 . Large variations were recorded for IgG concentrations (15.3-176.2 mg/ml) and yields (0.2-925 g). Cows in their first lactation produced significantl y lower concentrations and yields of colostral IgG than cows in later lacta tions. A colostral yield of IgG below the 100 g required to prevent calf hy po-gamma-globulinaemia was found in 18.3% of the cows. The concentrations o f IgG, beta-lg and BSB dropped abruptly in subsequent milkings and ct-la co ncentration decreased slowly. The mean IgG concentration was <2 mg/ml after eight milkings and <1 mg/ml after fifteen milkings. However, IgG concentra tion did not differ significantly, at the 1% level, during milkings 11-15. The results were tabulated to make it possible to calculate the excess of w hey proteins that would be obtained if early milks were illegally added to the milk supply.