Effects of different concentrations of monensin and monensin withdrawal upon the control of coccidiosis in the turkey.

The efficacy of different concentrations of monensin in turkeys exposed to field isolates of Eimeria and the effect of the withdrawal of monensin from their diet were investigated. Results of a battery study indicated that 66 ppm monensin was effective against three species of Eimeria in the turkey. In floor pens in which poults were exposed to infection, use of 59.5, 79.4, and 99.2 ppm monensin resulted in reduced mortality and improved feed conversion at 3 wk of age compared with birds that had received no medication. Poults given 59.5 ppm monensin weighed more and had a better feed conversion at 3 wk than poults given 79.4 or 99.2 ppm monensin, but at 10 wk no differences in the body weight or feed conversion of poults given different concentrations of drug were apparent. At 14 wk (and from 10 to 14 wk), poults that had been given 99.2 ppm monensin had a lower feed intake and weighed less than birds that had been given 59.5 ppm of the drug but there were no significant differences in feed conversion. There was no significant difference in the weight gain or feed conversion of poults from 10 to 14 wk of age whether monensin was present in the feed or had been withdrawn. No evidence of compensatory growth was found in the present study.