Two experiments were conducted to evaluate
lasalocid as a coccidiostat in Holstein calves and to compare
lasalocid with
monensin and
decoquinate. In experiment 1, calves in 3 groups (6 calves/group) were each inoculated with 500,000 sporulated oocysts, 88% of which were Eimeria bovis and 12% were E zuernii. Calves in each group were given
lasalocid-medicated feed at 0.50 (group 3), 0.75 (group 4), or 1 mg/kg (group 5) of
body weight/day for 45 days. Two control groups (6 calves/group) were also evaluated; calves in control group 2 were inoculated and nontreated, and calves in control group 1 were noninoculated and nontreated. At 0.50, 0.75, or 1 mg/kg/day,
lasalocid was equally effective in preventing induced
coccidiosis (E bovis and E zuernii) in calves. Compared with inoculated nontreated controls, treated calves had significantly (P less than 0.05) fewer oocysts in feces and had fewer clinical signs of
coccidiosis from days 16 to 30 after inoculation. Experiment 2 was conducted to compare the effectiveness of
monensin,
lasalocid, and
decoquinate for the prevention of experimentally induced
coccidiosis. Calves (n = 48) were allotted into 4 groups (12 calves/group); each was inoculated orally with 275,000 sporulated oocysts, predominantly E bovis and E zuernii, and each was given nonmedicated feed (group 6) or feed medicated with 33 mg of
lasalocid (group 7),
decoquinate (group 8), or
monensin (group 9)/kg of feed for 46 days. Calves given medicated rations had significantly (P less than 0.05) fewer oocysts in their feces and fewer clinical signs of
coccidiosis than did calves given nonmedicated rations.(ABSTRACT TRUNCATED AT 250 WORDS)