IgG and IgM levels in colostrum, milk and serum were quantitated by radial immunodiffusion. Concentration of milk IgG was found to be 65 mg/ml at the colostrum period. It further decreased to 3 mg/ml after Day 15 of lactation. However, the concentration of serum IgG was constant throughout the reproductive cycle (8-11 mg/ml). Concentrations of IgM in Serum and milk range between 0.5-1.5 mg/ml and 0.2-04 mg/ml respectively, with slight higher values in serum. Hence, IgG was rather used for offspring immunity than for the defense of the mammary gland.
