Effects of Baytril, Tylosin and Tiamulin on avian mycoplasmas.

The minimum inhibitory concentration (MIC) of Baytril, Tylosin and Tiamulin for strains of Mycoplasma gallisepticum (MG) M. synoviae (MS), M. meleagridis (MM) and M. iowae (MI) and serovars were compared. In general the lowest MIC for MG, MS and MI was obtained with Baytril, while for MM both Baytril and Tiamulin gave the lowest MICs. Protection against mortality was best attained with Baytril for broiler chicks and poults but against prevention of growth depression Baytril was best for broiler chicks whilst Baytril and Tylosin were equally effective in poults. MG was recovered from fewer birds following treatment with Tiamulin and then Baytril in that order. Baytril also had a suppressive effect on the natural infection of MI in poults. Fewer poults showed rapid serum agglutination reactions to MG antigen following Baytril treatment than with the other antimicrobials. The tolerance of turkey embryos for Baytril was between 1 and 2 mg/ egg. Baytril reduced MG infection of turkey embryos.