Efficacy of Stenorol (halofuginone). I. Against recent field isolates of six species of chicken coccidia.

The efficacy of Stenorol (halofunginone) was tested against six species of chicken Eimeria in a series of four battery experiments utilizing 3- to 4 1/2-week-old Cobb color-sexed broiler chickens. There were five replicates of eight chickens per replicate for each treatment of an experiment or a total of 1080 birds used in the study. The isolates were predominantly E. tenella, E. maxima, E. acevulina, E. necatrix, E. brunetti, or E. mivati and had previously been proven partially to totally resistant to several commercially available anticoccidial drugs. Halofunginone, at 3 ppm in the ration, was highly effective (P less than .01) against all six isolates as measured by weight gain at D+6 or +7and D+12 or +14 postinoculation; feed efficiency at D-2 to D+12 or +14; morbidity; mortality; dropping score; lesion score (D+6 or +7); and oocyst production during 4 or 5 days postinoculation (D = day of inoculation). The drug was not as effective against E. acervulina as against the other species, and increasing halofuginone to 4 ppm failed to improve activity of the drug signif;cantly against this isolate. However, 3 ppm of drug was effective against two other isolates of E. acervulina (from Alabama and Mississippi); 4 ppm was quite effective (P less than .01) in reducing dropping and lesion scores, but not significantly better than 3 ppm as measureed by other parameters. No relapse occurred after drug withdrawal and halofuginone was found to be cidal rather than static.