PSXI-8 - Heritability estimates of antibody- and cell-mediated immune response in North American Angus beef cattle

Including immune response traits in breeding programs has been suggested as a solution to improve overall animal health and enhance disease resistance but is not yet available for Angus cattle in North America. One way to measure immune response is to use the High Immune Response (HIR™) technology, which identifies animals with superior heritable immunity by evaluating antibody-mediated (AMIR) and cell-mediated (CMIR) immune response, allowing for the calculation of an estimated breeding value for total adaptive immune response for each animal. Before HIR™ can be included in beef cattle breeding programs, genetic parameters, including heritability, must be estimated for the traits involved. The objective of this study was to estimate a preliminary heritability for AMIR and CMIR in North American Angus beef cattle. On day 0 of the phenotyping protocol, cattle were immunized intramuscularly with a preparation of type 1 (CMIR) and type 2 (AMIR) antigens with adjuvant. On day 14, cattle received an intradermal injection of 0.1 mL of the CMIR test antigen in the right tail fold, and 0.1 mL PBS in the left tail fold. Change in cutaneous double skinfold thickness after 24 hours was used to assess CMIR. Blood was collected on days 0 and 14 to evaluate serum antibody to the type 2 antigen by ELISA to quantify AMIR. Heritability estimates were calculated for Canada and the USA separately, and then for both countries combined using single-trait animal models in ASReml and are presented in Table 1. The results of this study indicate that the heritabilities of AMIR and CMIR are moderate and emphasize the potential for its inclusion into Angus breeding schemes.