Monensin for the prevention of coccidiosis in calves.

Young calves (Holstein-Friesian) were inoculated with Eimeria bovis on the 3rd day after the start of 31 days' feeding of a ration containing added monensin in 2 dose levels: 16.5 g or 33 g/metric ton of feed. Monensin-treated calves were free of clinical signs of coccidiosis, but inoculated control calves developed diarrhea and had excessive oocyst discharge on days 19 to 28 after they were inoculated. Weight gains and feed efficiency in monensin-treated calves were equal or superior to those factors in noninoculated control calves for the 31-day period.