GWAS for Response to Vaccination to Bovine Respiratory Disease Complex in Angus Cattle

Bovine Respiratory Disease Complex (BRDC) results in losses greater than $800 million each yeah for the US cattle industry. Despite much research, effective treatments remain illusive and BRDC remains a major concern for producers. In this study, calves had antibody titer levels collected across multiple time points to measure response to vaccination against four viruses associated with BRDC (BVDV1, BVDV2, BRSV, BHV1). Five response traits were calculated for each virus (Initial Vaccination, Booster Vaccination, Booster Response, Initial Titer, Final Titer), while two additional traits (Pre-vaccination and Maternal Antibody Decay) were measured for BVDV1 and BVDV2 only. GWAS was performed on all measurement traits to identify regions of the genome associated with these traits. More than 1,400 individuals were imputed to 77k density (BovineGGPHD beadchip), and analyzed with BayesB with a pi of 0.975 (identification of the most effective 1,917 markers). Seven 1-mb SNP windows with the posterior probability of having non-zero genetic variance greater than 90% were identified as being associated with final antibody measurements. These windows accounted for 0.12% to 0.24% genetic variation. Other identified windows accounted for up to 3.5% of the estimated genetic variance. Response trait heritabilities ranged from 0.22 to 0.58. Final Titer score was also analyzed categorically (non-zero vs. zero titer score), resulting in heritabilities of 0.62 (BVDV1), 0.53 (BVDV2), and 0.59 (BHV1). Individuals with BRSV measurements had all non-zero titer scores and so could not be categorically analyzed. Although no single window accounts for large amounts of genetic variation, high heritabilities show the potential to select for animals with increased responses to vaccination.