Male Holstein calves were each inoculated with 350,000 sporulated oocysts of Eimeria bovis. Two calves were given
decoquinate (0.5 mg/kg of
body weight) continuously in dry feed for 29 days, and 2 calves each were given 0.5, 1, or 1.5 mg of
decoquinate/kg on an every 2nd-or 3rd-day schedule for 29 days. Calves given
decoquinate continuously did not discharge oocysts but had slightly loose feces. In general, the number of oocysts discharged increased and fecal consistency decreased as the time between feeding of medicated feed increased. Calves given 0.5 or 1.5 mg of
decoquinate/kg every 3rd day discharged more oocysts and had more
diarrhea than did calves given 1 mg of
decoquinate/kg every 3rd day. At postinoculation day 29, calves were euthanatized. At necropsy, intestinal tissues of calves given
decoquinate were mostly normal. Apparently, reduced
infections along with the elapsed time were sufficient to resolve most intestinal lesions caused by the coccidia.
Decoquinate was most effective when fed continuously at 0.5 mg/kg. However, when fed at 1 or 1.5 mg of
decoquinate/kg every 2nd day or 1.5 mg of
decoquinate/kg every 3rd day, oocyst production was reduced and clinical
coccidiosis was prevented.