Effect of monensin on experimental infections of Eimeria ninakohlyakimovae in lambs.

Two nearly identical experiments were conducted to determine the effects of the coccidiostatic compound monensin on Polled Dorset lambs experimentally infected with oocysts of Eimeria ninakohlyakimovae. Prophylactic medication at a dose level of 1 mg/kg of body weight was started 2 days before inoculation and prevented diarrhea and reduced oocyst production. Therapeutic medication at a dose level of 2 mg/kg, started with the appearance of signs of infection, reduced oocyst production below that of nonmedicated controls but did not eliminate diarrhea. Weight gains of medicated lambs were less than those of noninoculated, nonmedicated controls in both experiments. Apparently monensin, at the dose levels used, reduced oocyst production but also prevented weight gains as high as those in inoculated nonmedicated controls.