Clinical effectiveness of tulathromycin, a novel triamilide antimicrobial, for the control of respiratory disease in cattle at high risk for developing bovine respiratory disease.

The efficacy of tulathromycin in decreasing the incidence of morbidity and mortality due to bovine respiratory disease (BRD) in 1,239 high-risk cattle was investigated at four US feedlots. Calves not exhibiting clinical signs of BRD received one of three treatments administered subcutaneously in the neck: physiologic saline at 0.02 ml/kg, tulathromycin at 2.5 mg/kg, or tilmicosin at 10 mg/kg. Each treatment group consisted of 413 calves. Calves with clinical signs of BRD and rectal temperatures of 104 degrees F or higher on days 1 through 14 were considered treatment failures (BRD morbidity). Nasopharyngeal swabs from saline-treated morbidities were submitted for isolation and identification of BRD organisms. Respiratory disease morbidity was highest in calves treated with saline and significantly (P < or = .0001) lower in calves administered tulathromycin or tilmicosin. Morbidity from BRD was significantly (P < or = .0001) higher in calves treated with tilmicosin than in calves treated with tulathromycin. Under conditions of this study, tulathromycin, given to calves at high risk of developing BRD, was significantly more effective in reducing BRD morbidity when compared to both saline- and tilmicosin-treated calves.