Comparative investigation on the efficacy of tulathromycin and florfenicol in the treatment of bronchopneumonia in feedlot calves

The clinical efficacy of tulathromycin (TU) and florfenicol (FL) in the treatment of bronchopneumonia (BP) caused by Pasteurella multocida which was isolated from nose swabs of diseased calves has been examined. The symptoms of bronchopneumonia (BP) were quantified by means of the clinical score (CS) with a maximum of 47 points. In the current investigation the average CS in diseased calves was 23.5? 0.15. The clinical efficacy of TU and FL was assessed every day in the first week after the administration of the drugs and was based on the decrease in CS and on microbiological findings on days 7, 28 and 35 after the completion of therapy. Tulathromycin was administered s.c., in the prescribed therapeutic dose (2.5 mg/kg BW), and florfenicol s.c., twice at a 48 h interval, in its respective therapeutic dose (40 mg/kg BW). In spite of the repeated administration of FL, TU was significantly more rapid to decrease the major clinical symptoms in the first four days following the application, in comparison with FL (P<0.05). On the fourth day after the administration, the clinical efficacy of TU in the therapy of BP in calves was 43.4?1.5 %, and of florfenicol 27.2?1.6 %. However, five days after the application of TU and two days after the repeated application of FL the assessed clinical efficacy of the two antibiotics was roughly the same. The average efficacy of TU was 57.1?0.0%, and of florfenicol 58.5?0.0%, both the individual and mean CS in the treated calves was 10 points, due to hyperthermia, which remained the only symptom. Six days after the administration of TU and three days after the repeated application of FL both antibiotics had equal maximum efficacy (100%) in the treatment of BP. The clinical efficacy remained unchanged on day seven. The recovery was confirmed by the absence of P. multocida in nose swabs sampled on the seventh day after the initial treatment. However, in 4 calves (21.05 %) of the 19 treated Streptococcus alpha haemolyticus was isolated. Four weeks after the completion of the treatment with TU and FL the recurrence of BP caused by P. multocida was noted in 30% of calves treated with TU and 22.22% with FL. Seven days after a single administration of TU and FL, all clinical symptoms of recurrent BP and the microbiological findings were negative. Given the obtained results of the investigation on the efficacy of TU and FL in calves, TU can be recommended as the drug of first choice in the treatment of BP caused by P. multocida. Its insufficient clinical efficacy in the first three days following the application may be enhanced by simultaneous administration of NSAID and bronchodilators.