F02 - Serum IgG and Specific Immunity in Calves Fed 300g of IgG from a Colostrum Replacer

Abstract: Background- It is unclear if colostrum replacement with 300g of IgG results in excellent serum IgG (> 25 g/L) and specific antibody concentrations in dairy calves. Hypothesis/Objectives- Feeding 6L of maternal colostrum or 300g of IgG from a colostrum replacer will result in excellent serum IgG and specific antibody concentrations. Animals- 48 newborn dairy calves. Methods- Calves were assigned at birth to one of four colostrum treatments. A colostrum replacer providing 300g IgG was fed either in two equal doses within 6h of birth (CR1, n = 12) or as a single dose within 2h (CR2, n = 12). Maternal colostrum (6L) was fed within 12h of birth and was obtained from cows either not re-vaccinated at dry-off (MC1, n = 12) or re-vaccinated at dry-off (MC2, n = 12). Total IgG concentrations and BVDV1a and BHV-1 antibodies in colostrum and serum were evaluated. Results- Excellent serum IgG concentration occurred in 91.6% (11/12) of MC1 calves and 100% (12/12) of MC2 calves, but in none of the CR1 or CR2 calves. Most calves in the CR groups achieved fair serum IgG (10–17.9 g/L), occurring in 83.3% (10/12) of CR1 calves and 63.6% (7/11) of CR2 calves. Despite these differences, mean log₂ BVDV1a and BHV-1 antibody titers in MC and CR, and 48h calf serum did not differ among groups. Conclusions and Clinical Importance- Colostrum replacement with 300g of IgG did not result in excellent transfer of passive immunity but provided significant antibody concentrations against BVDV1a and BHV-1.