EFFECT OF BENTONITE INCORPORATED IN A FEED RATION WITH TILMICOSIN IN THE PREVENTION OF INDUCED MYCOPLASMA-GALLISEPTICUM AIRSACCULITIS IN BROILER-CHICKENS

A factorial arrangement of tilmicosin and bentonite was evaluated for efficacy in broiler chickens infected with Mycoplasma gallisepticum an d correlated to tilmicosin recovery in a feed assay method. Tilmicosin at 300-500 g/ton prevented development of airsacculitis. The addition of 2% bentonite to the ration caused tilmicosin at 300 g/ton to be in effective in controlling air-sac lesions, whereas 400 and 500 g/ton we re moderately effective. Six percent bentonite rendered tilmicosin com pletely ineffective at all dose levels. There was a direct correlation between the percentage of bentonite in the feed rations, the percenta ge of the tilmicosin recovered in the assay procedure, and the increas ed incidence of air-sac lesions.