Prophylactic Efficacy of Enrofloxacin and Tilmicosin on Bovine Respiratory Disease in Newly Arrived Beef Cattle Associated with Pasteurella multocida and Mycoplasma

When introduced to a large-scale beef-cattle farm where outbreaks of respiratory disease had frequently occurred, clinically healthy 10-month-01d Japanese Black cattle and 7-month-old FI cattle received subcutaneous injections of either a mixed vaccine plus enrofloxacin (ERFX group, n=401) or a mixed vaccine plus tilmicosin (TMS group, n=501); and the effects of the inoculations in preventing the onset of respiratory disease were studied. Results were compared with those from cattle receiving the vaccine only (control group, n=236). Incidence of respiratory disease in the ERFX and TMS groups were significantly (P<0.01) lower than in the control group. Three days after injection, bacteriologic tests showed that Pasteurella multocida iso-lation rates were remarkably higher in the control group than in the ERFX and TMS groups. P. multocida and Mycoplasma spp. were isolated from nasal swabs taken when the cattle were introduced to the farm. Both proved highly sensitive to ERFX, although most strains of Mycoplasma spp. resisted TMS.