Efficacy of a DNA immunostimulant for on-arrival control of bovine respiratory disease in fall-placed feedlot calves

A randomized complete block design trial was conducted in a commercial finishing feedlot in southern Alberta, Canada using auction-market origin fall-placed steer calves (n = 5430; initial body weight 618 ± 22 lb; 280.9 ± 10.0 kg) to evaluate the comparative efficacy of on-arrival treatment with a DNA immunostimulant and tulathromycin versus tulathromycin alone for prevention of bovine respiratory disease (BRD). The addition of the DNA immunostimulant reduced first-pull treatment rates for BRD (P=0.02), case fatality rate for BRD (P=0.08), mortality rate for BRD (P=0.03), mortality rate for BRD and histophilosis (P=0.09), average daily gain (P<0.01) with dead weights included, and increased dry matter conversion (P<0.01) with dead weights included.