LAUSR

Abstract Bovine respiratory disease (BRD) is often diagnosed in feedlots after observing behavioral changes such as anorexia, with fever confirmatory. However, this method has poor diagnostic accuracy compared to postmortem lung lesions. Little is known about how these or other sickness responses such as low grooming present in early, spontaneous BRD, especially during feedlot acclimation. To inform improved detection, we studied 3 aspects of the BRD sickness response at and before diagnosis and the effect of acclimation on behavior in beef heifers. We hypothesized that heifers with BRD would have fever and spend less time feeding and grooming compared to controls, and that both behaviors would increase with acclimation. Beef heifers were randomized to replicate and pen, balanced for body weight (total n = 80), and monitored for 12 d, starting 2 d after shipping. Rectal temperature was measured with a logger, while feeding time and brush use were video-recorded. Clinical signs were recorded daily: heifers remaining healthy over the entire 12 d were Controls (n = 46); those meeting set criteria were classified as BRD (n = 21). Health effects were analyzed for all 3 dependent variables on the day of diagnosis (d 0), and for fever and feeding, the 2 days before (d −1 and −2), using analogous days for Controls. Acclimation effects were tested separately using all available behavioral data. BRD heifers had a fever on d 0 and −2 (≥0.4 °C higher than Control, P