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Chickens infected with any one of the six major species of chicken coccidia had lower levels of blood carotenoids (plasma pigmentation) than did uninoculated control birds. The species were Eimeria acervuUna, E. mivati, E. maxima, E. necatrix, E. brunetti, or E. tenella. Carotenoids decreased as early as 4 days postinoculation (PI) (E. acervuUna), but returned to a normal level by 14 days PI (E. mivati, E. acervuUna, and E. tenella). The maximum decrease occurred at 7 or 8 days PI in all species and was 49.8% with E. tenella and 62.4%-74.0% with the five intestinal species. Additional studies with E. tenella, E. acervuUna, and E. brunetti indicated that the magnitude of the decrease was related to the number of oocysts given within any one species. Increasing oocyst number also resulted in a more rapid reduction of longer duration in carotenoid levels.

Infections with single species of Eimeria acervulina, E. mivati, E. maxima, E. tenella, E. necatrix, and E. brunetti, and the six species mixed, were utilized in three separate battery experiments to evaluate the anticoccidial efficacy of various levels of salinomycin (AHR-3096), a fermentation product of a strain of Streptomyces albus. At the 60 to 100 p.p.m. treatment levels, this compound showed significant anticoccidial activity for all parameters studied (mortality, weight gain, feed conversion, dropping scores, and lesion scores). The mortality due to coccidiosis was reduced to 0.1% in the medicated infected birds. Some activity, as measured by weight gain, was seen in the lower levels of salinomycin medication (12.5 to 50 p.p.m.), but other parameters, including mortality and lesion scores, indicated less activity than that seen with the higher treatment levels. At 100 p.p.m., there was no apparent effect on the compound on bird performance in uninfected control birds. Salinomycin at the 100 p.p.m. treatment level was statistically as effective as 121 p.p.m. monensin (reference anticoccidial) in controlling coccidiosis.

Three floor-pen trials were conducted to compare two attenuated strains of Eimeria tenella (Wis-F-96 and Wis-F-125) with the strain of E. tenella used in a commercial planned immunization program (Coccivac). Broiler cockerels were started in floor pens on new pine shavings litter. Immunizing oocysts were administered in the drinking water during the first week with total dose per bird of 175 oocysts of the control strain (Coccivac); 175, 350, or 700 oocysts of the Wis-F-125; 350 oocysts of Wis-F-96; or no oocysts (non-seeded control). The control strain was more pathogenic than the Wis-F-125 or the Wis-F-96 strains as indicated by significantly higher lesion scores 17 days after initial exposure and by loss of two birds in the control strain exposed groups. Low lesion scores and no deaths due to coccidiosis characterized the use of the Wis-F-125 strain. Flock immunity, as determined by immunity challenge, was equivalent between the control strain and the higher dosages of Wis-F-125. The Wis-F-96 strain did not adequately immunize chickens in these experiments.

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