EVALUATION OF FLORFENICOL FOR THE TREATMENT OF UNDIFFERENTIATED FEVERIN FEEDLOT CALVES IN WESTERN CANADA

A study was conducted in western Canada to evaluate the efficacy of fl orfenicol for the treatment of undifferentiated fever (UF) in feedlot calves, One hundred and twenty-five recently weaned, auction market de rived, crossbred, beef steer calves suffering from UF were allocated t o 1 of 2 experimental groups as follows: florfenicol, which was: intra muscular florfenicol administered at the rate of 20 mg/kg body weight at the time of allocation (day 0) and again 48 h later; or control, wh ich was intramuscular saline administered at the same volume as florfe nicol at the time of allocation and again 48 h later. Eighty-four calv es were allocated to the florfenicol group and 41 calves were allocate d to the control group. Outcome measures describing animal health, bod y weight, and rectal temperature parameters were used to deter mine th e efficacy of florfenicol for the treatment of UF. The 1st relapse of UF, 2nd relapse of UF, overall mortality, bovine respiratory disease m ortality, and haemophilosis mortality rates were significantly (P < 0. 05) lower in the florfenicol group than in the control group. Animals in the florfenicol group were significantly (P < 0.05) heavier at day 15 and day 45 than animals in the control group. The rectal temperatur e on days 1, 2, 3, and 4 of animals in the florfenicol group was signi ficantly (P < 0.05) lower than in the control group. In addition, the change in rectal temperature from day 0 to day 4 was significantly (P < 0.05) different between the experimental groups. The results of this study demonstrate that florfenicol is an efficacious antimicrobial fo r the treatment of UF.