The anticoccidial activity of semduramicin against laboratory isolates of five species of poultry Eimeria was investigated. In laboratory scale battery trials, semduramicin at 20 to 30 ppm demonstrated broad-spectrum anticoccidial efficacy equivalent to salinomycin at 60 ppm. Also, semduramicin at 25 ppm was fed to uninfected cockerels in batteries for 21 days, and growth rate and feed efficiency were found to be equivalent to birds fed salinomycin at 60 ppm. Semduramicin was well tolerated when coadministered with tiamulin. Semduramicin demonstrated the same activity whether produced by semisynthesis or by direct fermentation.
Salinomycin (Coxistac), a new broad spectrum anticoccidial, was tested in broilers reared in floor pens for safety at 50, 60, 80, 100, and 160 ppm fed continuously from 1 to 56 days of age. Four trials were conducted. Comparisons were made to unmedicated controls and in three trials to monensin to monensin at 80, 100, and 121 ppm. The weight gains at 50 and 60 ppm of salinomycin and 80 and 100 ppm of monensin were statistically comparable and equivalent to or better than controls. The weight gain at 80 ppm of salinomycin was slightly below controls but comparable to 121 ppm monensin. Levels of 100 and 160 ppm of salinomycin depressed weight gain. Feed conversion for all treatments except 160 ppm salinomycin were comparable.
The efficacy of danofloxacin was compared with that of tylosin in the control of induced mycoplasmosis. In three experiments, disease was induced in broiler chicks by intrapulmonary injection of field isolates of Mycoplasma gallisepticum (MG) originating from Brazil, a different isolate being used for each experiment. Starting the day after inoculation, groups of chicks were medicated for 3 days via the drinking water with danofloxacin (50 ppm) or tylosin (500 ppm) or were left as unmedicated controls. Chicks were observed for 21 days. A severe mycoplasmosis was induced in unmedicated birds, characterized by mortality, depression, and respiratory signs. Danofloxacin was highly efficacious in controlling this infection in all three experiments, whereas tylosin was efficacious in only one. This difference could be related directly to the reduced in vitro susceptibility to tylosin displayed by the two isolates of MG. In the two experiments where isolates were tylosin-resistant, danofloxacin was significantly (P < or = 0.05) superior to tylosin in reducing mortality, maintaining weight gain, and reducing the prevalence of air-sac lesions, isolation of MG, and seroconversion.
Broiler chicks were given salinomycin in the feed at levels of 30 and 60 ppm in battery trials to measure the efficacy against six major species of Eimeria. Comparisons to nonmedicated chicks (controls) and chicks given monensin at 50 and 100 ppm or lasalocid at 37.5 and 75 ppm were made. Factors measured were the severity of coccidia lesions, mortality, and weight gain. The efficacy of salinomycin, monensin, and lasalocid in preventing lesions differed in many respects. The lesion control of salinomycin at 60 ppm was excellent against E. acervulina, E. mivati, E. necatrix, and E. tenella, and slightly reduced against E. maxima and E. brunetti. The lesion control of monensin at 100 ppm was excellent against E. mivati and E. necatrix, and slightly reduced against E. tenella, E. acervulina, E. maxima, and E. brunetti. The lesion control of lasalocid at 75 ppm was excellent against E. brunetti, slightly reduced against E. maxima, E. necatrix, and E. tenella, and lowest against E. acervulina. Based upon all measurements, salinomycin at 60 ppm was comparable or superior to monensin at 100 ppm and lasalocid at 75 ppm. At 30 ppm, salinomycin was more effective overall than monensin at 50 ppm or lasalocid at 37.5 ppm. The relative potency of each anticoccidial agent was clearly evident in these data.
Experimental mycoplasmosis was induced in 1-day-old chicks by intrapulmonary inoculation of Mycoplasma gallisepticum (MG). This method of infection proved to be useful for evaluating the efficacy of antimicrobial medication, by measuring mortality, weight gain, pathological responses, frequency of reisolation of MG, and seroconversion. Using this model, the efficacies of danofloxacin (a novel fluoroquinolone) and tylosin were compared for two MG isolates, a reference isolate (the R-strain) and a field isolate from California. Danofloxacin administered in the water at 50 ppm for 3 days was equivalent to tylosin at 500 ppm for 3 days in the degree of control of mortality and maintenance of weight gain. Danofloxacin was superior to tylosin in preventing air-sac lesions, reducing the frequency of reisolation of MG, and preventing seroconversion in surviving birds.
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