Evaluation of passive transfer, apparent efficiency of absorption and health in dairy calves

Abstract: Calves are born without preformed antibodies and are dependent on colostrum to acquire passive transfer of immunity from their mother. Failure of passive transfer (FPT) is a contributing factor to increased calf mortality and morbidity, and hence of economic importance to the producer. The level of passive transfer (PT) is associated with future health and productivity even in adult age. Several factors that influence the level of passive transfer in the calf are well studied, especially the importance of colostrum quality. The role of efficiency of absorption in the calf is less well understood. The aim of this study was to determine serum immunoglobulin G (S-IgG) by an enzyme-linked Immunosorbent assay (ELISA) newly established in our lab, estimate apparent efficiency of absorption (AEA) of 803 calves from two Swedish farms and investigate how they affected calf health and FPT. An ELISA protocol was established in our laboratory to determine S-IgG concentration of 700 calves at 2-7 days of age and AEA was calculated. The ELISA S-IgG values were correlated to serum total protein (STP) measured by an optic refractometer (n=224) with r=0.75 (p<0.0001) for Spearman´s rank correlation coefficient. Despite a good correlation, the ELISA was likely to overestimate S-IgG concentration and this probably affected the proportion of FPT. Proportion of FPT was clearly lower than previous study partly using the same samples (De Haan, 2018). The FPT for Lövsta was found to be 9.5% and for Röbäcksdalen 30.4%, compared to previously 16% and 44.7%, respectively. AEA range and mean of the farms were very similar, but there was a greater difference in mean S-IgG between the farms. Mean AEA of calves classified in our study to have FPT was significantly lower than the total average AEA of calves from the same farm. Surprisingly, both mean S-IgG concentration and AEA were significantly lower for healthy calves than unhealthy calves. This comparison included only calves from Lövsta, which had relatively few and mild cases of illness. Röbäcksdalen did not have sufficient data available to be included. Birth weight and amount of IgG fed first meal were not significantly correlated to AEA in this study.