Field Efficacy Evaluation of Gamithromycin for Treatment of Bovine Respiratory Disease in Cattle at Feedlots

Bovine respiratory disease (BRD) complex is the most common disease occurring in feedlot cattle. Vaccines and antibiotics remain the standard methods for prevention, control, and treatment. Gamithromycin is an azalide 15-membered semi-synthetic macrolide antibiotic that has been developed for treatment and prevention of BRD in feedlot cattle. Cattle, clinically ill with BRD, treated with gamithromycin at 6 mg/kg (2mL/50kg) by subcutaneous injection on Day 0, had significantly (P<0.05) lower mean depression scores, respiratory character scores, and rectal temperatures on daily assessments on Day I through the completion of the 10-day study than negative control cattle treated with saline. The percentage of overall treatment successes for cattle treated with gamithromycin was significantly (P<0.05) higher than in the control cattle treated with saline. Mortality also was significantly lower for cattle treated with gamithromycin (0.6%) than for control cattle treated with saline (8.5%). These results indicate that a single dose of gamithromycin at 6 mg/kg (2mL/50kg) is significantly effective as a treatment of for cattle showing clinical signs of BRD.