Selective absorption of immunoglobulin IgM in the newborn calf

The efficiency of absorption of colostral immunoglobulin classes was determined by the ratio of the quantity of immunoglobulins in the calf serum after absorption was complete to the quantity in the colostrum fed the calves. The experiment with 58 pooled colostrums assayed for absorbability of immunoglobulins had three to eight calves per assay. Colostrums with similar concentrations of immunoglobulins varied from 10 to 46% in absorption of IgG and 5 to 50% in IgA. The percent of immunoglobulin IgM absorbed increased as the amount ingested decreased. The absorption efficiencies of immunoglobulins IgA and IgG did not change as intake varied. Correlations of colostral immunoglobulins ingested with percent absorption in summaries of two experiments were -.76 and -.90 for IgM, 0 and -.33 for IgG, and -.05 and -.02 for IgA. The selective transport of IgM is important for its role as the primary immunoglobulin giving the calf immune protection during the first few days of life. The variation in absorption of IgM in different colostrums of similar immunoglobulin content was not different from that among calves receiving the same colostrum.