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

Abstract

Colostrum and milk samples from 20 goats were analysed for concentrations of immunoglobulin G (IgG), beta-lactoglobulin (beta-lg), alpha-lactalbumin (alpha-la) and serum albumin (CSA) throughout the first 14 milkings post partum (7 d of lactation) using single radial immunodiffusion assay. Concentrations (mg/ml, means +/- SD) at first milking were IgG 47.9 +/- 25.5, beta-lg 30.7 +/- 10.4, alpha-la 2.77 +/- 0.82 and CSA 2.97 +/- 2.46 mg/ml. Large variations were recorded for IgG concentrations (19.9-94.5 mg/ml) and beta-lg (9.3-49.8 mg/ml). Concentrations of IgG, beta-lg and CSA dropped abruptly in the subsequent milkings and alpha-la concentration decreased slowly. Mean IgG concentration was < 2 mg/ml after 7 milkings and < 1 mg/ml after 11 milkings. However, IgG concentration does not differ significantly, at the 1% level, from milkings 7-14. The contribution of beta-lg to the increase in whey proteins in early milks was greater than that of IgG from milkings 5 to 14. The results were tabulated to make it possible to calculate the excess of whey proteins that would be obtained if early milks were illegally added to milk supply.