Type 1 and type 2 immune response profiles of commercial dairy cows in 4 regions across Canada.

Diseases of dairy cattle have adverse implications for both the dairy industry and animal welfare. Understanding adaptive immune response profiles of cattle on a national scale will provide insight into the potential for improving health and decreasing disease. The objectives of the present study were to evaluate immune response phenotypes of Holstein cows outside the peripartum period and to determine if antibody isotype bias to putative type 1 and type 2 test antigens is maintained. The cows, housed on commercial farms in 4 key dairy regions across Canada, were immunized with test antigens to measure their ability to mount cell-mediated immune responses (CMIR) and antibody-mediated immune responses (AMIR). Delayed-type hypersensitivity (DTH) was used as an indicator of CMIR and primary and secondary serum antibodies of the immunoglobulin (Ig) G1 and IgG2 isotypes were used to determine AMIR to the test antigens. Immune response phenotypes varied significantly among regions, herds, and cows. Cows in Alberta had significantly higher DTH responses and secondary responses to the type 2 test antigen than those in other regions. However, cows in Alberta had significantly lower primary antibody responses. It was found that Alberta had the lowest incidence of mastitis caused by Escherichia coli and Staphylococcus aureus compared with other regions. The IgG1/IgG2 antibody isotype ratio confirmed the nature of the test antigens. This was the first study to evaluate adaptive immune response profiles and disease incidence of dairy cows on a national scale and it therefore provides a glimpse of the current situation in Canada.