Age and Previous Lactations as Factors in the Amount of Bovine Colostral Immunoglobulins

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Abstract
Blood and colostrum samples were obtained from 87 dairy cows in 5 lactation groups and analyzed for IgG1, IgG2, IgM and IgA. The 5 groups ranged from cows in 1st lactation, .apprx. 30 mo. of age, to cows in 5th or more lactation, .apprx. 84 mo. of age. Compared to older groups, serum of cows in 1st lactation contained less IgG1. Cows in 1st lactation also produced less total colostrum containing less total IgG1, IgG2 and IgM. IgG1 comprised over 2/3 of the Ig in the colostrum of all groups. Older cows had more IgG1 in their colostrum with a tendency toward a higher ratio of IgG1 to IgG2. Amount of IgA was constant through all lactations. After a rise in the 2nd lactation, total amount of IgG2 and IgM tended to level off. Total IgG1 tended to reach a maximum in the 3rd or 4th lactation, almost doubling in amount compared to the 1st lactation. Age and number of lactations are factors correlated with amounts of these Ig in colostrum.