Adaptive immune response, survival, and somatic cell score between postpartum Holstein and Norwegian Red x Holstein first-calf heifers

The objectives of this study were to evaluate antibody (AMIR) and cell-mediated immune responses (CMIR), survival, and somatic cell score (SCS) between purebred Holstein (HO) and crossbred Norwegian Red x Holstein (NRHO) first-calf heifers postpartum. Additionally, immune response traits observed as calves in a previous study were correlated with their immune response traits as first-calf heifers. Heifers, previously immunized as calves, were bled and reimmunized 6 to 9 d postcalving with known type 1 and type 2 antigens and human serum albumin (HSA). Seven days later, heifers were rebled, and background skinfold measurements of the tail fold were taken. Intradermal injections of PBS and type 1 antigen were administered on either side of the tail fold. On d 9 final skinfold measurements were taken and used to assess delayed-type hypersensitivity (DTH) as an indicator of CMIR. Blood samples were also collected for a final time on d 14 from heifers that received the antigen HSA. Serum was obtained from blood collected on d 0, 7, and 14 and analyzed by ELISA to assess AMIR. Data on survival and somatic cell count, which was converted to SCS, were obtained from CanWest Dairy Herd Improvement (DHI). All SCS, survival, and immune response data were analyzed using general linear models to determine significance between HO and NRHO first-calf heifers. To determine residual correlations between immune response traits observed in calves to their responses as first-calf heifers, residuals were obtained from models, and correlations between traits were determined using PROC CORR in SAS. Results showed NRHO had a greater primary IgG antibody response to HSA and greater tertiary IgG antibody response to the type 2 antigen compared with HO. Crossbreds (NRHO) also had significantly greater DTH response (P < 0.05) and, in general, greater survival from calving to 100 d in milk (dim), 100 to 305 dim, calving to 305 dim, and age at immune response testing as calf to 305 dim. No difference was observed between breeds for SCS. Results also showed most correlations between calf and first-calf heifer immune response traits were found to be positive and significant (P < 0.05). In conclusion, NRHO heifers have greater survival, which likely relates at least in part to increases in aspects of both AMIR and CMIR and could indicate that crossbred heifers have enhanced disease resistance.