Efficacy of florfenicol against Mycoplasma gallisepticum infection in broiler chicken

The minimal inhibitory concentrations(MIC S) of florfenicol and enrofloxacin against Mycoplasma gallisepticum(MG) were determined by two-fold dilution,the MIC of florfenicol and enrofloxacin were respectively 1.25, 0.019 5 mg/L.The in vivo test showed that florfenicol given respectively at 300,400 and 500 mg/kg in feed additive for 5 successive days exhibited significantly protection in broiler chicken infected with MG but mortality of untreated group was 25%(P0.01).The weight gain of groups treated with florfenicol and enrofloxacin were significantly higher than that of the positive control(P0.01).The groups treated with a dosage of 400-500 mg/kg of florfenicol reduced significantly air sac lesions scores(P0.01).However,all groups treated with florfenicol did not reduce the positive serum agglutination reaction,in contrast to the positive group.