High immune responder cows have lower treatment risk and reduced milk loss during highly pathogenic avian influenza H5N1 outbreaks

The spillover of highly pathogenic avian influenza (HPAI) hemagglutinin type 5 and neuraminidase type 1 (H5N1) into dairy cattle marks the emergence of a new threat to herd health and production efficiency for North American dairy cattle. To address this challenge, this study evaluated whether genetic selection for improved immune response, using Immunity+ GEBVs, can increase resilience to HPAI H5N1 in commercial dairy herds. Treatment records (n = 15,386) and daily milk yield data (n = 650) were obtained from herd management software from 6 large commercial dairy herds in the United States with confirmed HPAI H5N1 outbreaks. The association between Immunity+ GEBV classes and the likelihood of requiring supportive treatment was assessed using binomial logistic regression, while linear models were used to assess the effects of Immunity+ GEBV class on the length of the milk fluctuation period following treatment and total milk loss during this period. Cows with high Immunity+ GEBVs were 24% less likely to require supportive treatment compared with those with low Immunity+ GEBVs (odds ratio = 0.76; 95% CI: 0.64 to 0.9). High immunity cows also experienced significantly lower milk loss (484.46 kg; 95% CI: 440.61 to 528.30 kg) during the post-treatment fluctuation period compared with low immunity cows (618.10 kg; 95% CI: 561.08 to 675.12 kg). Overall, these findings support the value of selecting for enhanced immune response to improve animal health, reduce production losses, and strengthen economic resilience during disease challenges.