No abstract

A factorial arrangement of tilmicosin and bentonite was evaluated for efficacy in broiler chickens infected with Mycoplasma gallisepticum and 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 ineffective in controlling air-sac lesions, whereas 400 and 500 g/ton were moderately effective. Six percent bentonite rendered tilmicosin completely ineffective at all dose levels. There was a direct correlation between the percentage of bentonite in the feed rations, the percentage of the tilmicosin recovered in the assay procedure, and the increased incidence of air-sac lesions.

A method was developed and validated for determination and quantitation of tilmicosin residues in swine, cattle, and sheep edible tissues, as well as chicken fat, skin, and muscle over a concentration range of 0.025 μg/g–20 μg/g. For chicken kidney and liver, the method was validated over a range of 0.060 μg/g–20 μg/g. The tissue sample was extracted with methanol and a C18 cartridge was used for solid-phase extraction cleanup. A reversed phase gradient liquid chromatographic method with detection at 280 nm was used to separate the tilmicosin from matrix components in 30 min run time. The limit of quantitation (LOQ) of the method was 0.025 μg/g for all tested tissues except chicken kidney and liver, for which the LOQ was 0.06 μg/g. Average recoveries for tissue samples ranged from 73 to 98%. Relative standard deviation values ranged from 0.6 to 14.7%.

A series of homologous IV ,/V'-bls(2,4-dinltrophenyI )-a,