(1) DC-45, an ethyl substitute in 2-position of the pyrimidine ring of dimethialium, administered continually at a level of 16 ppm, the lowest concentration tested, had an excellent prophylactic effect against
Eimeria tenella infection in chickens. Feeding of DC-45 at 31 ppm was practically effective against
E. necatrix, and at 125 ppm against
E. brunetti or
E. acervulina, judging from the severity of intestinal lesions, weight gains, and counts of oocysts passed.
(2) Ten ppm of thiamine in feed produced no significant reduction in anticoccidial activity of DC-45 provided at a level not less than 31 ppm. When DC-45 was given at a level of 16 ppm, mild hemorrhage and cecal lesions were observed, but oocysts passed increased in number.
(3) There was a marked decrease in oocyst production of
E. tenella in chickens fed a thiamine deficient diet. In chickens infected with
E. brunetti and
E. acervulina and fed a thiamine-deficient diet, oocyst output was reduced to a moderate and a small extent, resperc tively.
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