Absorption and endogenous production of immunoglobulins in calves.

Abstract

SummaryThe changes in the concentration of IgG1, IgG2, IgM and IgA were measured in the blood serum of 7 calves from birth to 18 weeks of age. The previously unsuckled calves were each fed 2 l of their dam's colostrum within the first six hours after birth.IgG1 and IgG2 were present in low concentrations in the sera of all calves before first suckling, IgM was found in 5 calves and IgA in only 2. Peak serum concentrations of IgM and IgA were observed twelve hours after first feeding colostrum, whereas IgG1 and IgG2 did not reach peak concentrations until twenty four hours. It was estimated that IgM was absorbed with an efficiency of almost 100%. The considerably lower apparent efficiencies of absorption for IgG1 and IgG2 were attributed to loss of these lower molecular weight immunoglobulins into the interstitial fluid.The initial increase in concentration of all four immunoglobulins was followed by a linear decline during the subsequent 8–16 days; this was taken to represent biological degradation. Regression coefficients for IgG1 and IgG2 were significantly less than those for IgM and IgA, reflecting the more rapid disappearance of IgM and IgA from the circulation.The results indicated that significant endogenous production of IgG1, IgG2and IgM began 8–16 days after birth and around 64 days for IgA.