[Coccidiosis in lambs: observations in the preventive use of an amprolium-containing medicated feed].

The efficacy of preventive in-feed medication with amprolium (2000 ppm) was studied on a farm where clinical coccidiosis in unweaned lambs at pasture has been a problem for the past seven years. Both treated and untreated control lambs had access to the concentrates through creep feeding. In this clinical trial neither the treated group (15-17 mg of amprolium per kg body weight per day for three weeks) nor the control group showed clinical symptoms of coccidiosis. It seems likely that this is attributable to the feeding of concentrates. Nevertheless, the excretion of oocysts by the animals of the treated group was significantly lower than that of the control group. An outbreak of clinical coccidiosis in another group of lambs on this farm was successfully controlled by single drenching, 50 mg.kg-1, followed by the medicated feed. The pharmaceutical availability of amprolium in the concentrates was 95 +/- 1% immediately after preparation and the stability during storage under field conditions for two months was 100% +/- 2%.