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Specific-pathogen-free (SPF) chicks infected with infectious bursal disease (IBDV) virus at one day of age or midway (7 days) through a two-week immunization program for Eimeria tenella showed significantly less (P less than or equal to 0.05) protection against coccidal challenge as measured by lesion scores than chicks given IBDV after 14 days of coccidial immunization. The chicks showed complete protection to later coccidial challenge administered on Day 21. Bursae were markedly smaller from IBDV-infected chicks than from uninfected controls, and pathological changes were extensive. Virus-neutralization tests demonstrated that titers to IBD were higher in chicks exposed to the virus than in unexposed controls.

New combinations of techniques were employed for comparing the development of immunity of Eimeria tenella in chickens being medicated with 12 different anticoccidials. Broiler-type birds in batteries received a daily measured dose of E. tenella oocysts for 15 consecutive days while the drug was administered at the manufacturer's recommended level. Two or more tests of each drug gave the following ratings: strong suppression, monensin (121 ppm), salinomycin (80 ppm), lasalocid (75 ppm); moderate suppression, monensin (100 ppm), decoquinate (30 ppm), clopidol (125 ppm), and narasin (80 ppm); slight suppression, arprinocid (70 ppm), nicarbazin (125 ppm), and amprolium (125 ppm + ethopabate (4 ppm); no effect, robenidine (33 ppm), zoalene (125 ppm), and aklomide (250 ppm).

Monensin at 60, 80, or 100 ppm in feed reduced mortality and lesion scores while protecting against weight loss of turkeys infected with the major pathogenic species: Eimeria adenoides, E. meleagrimitis, and E. gallopavonis. With single and mixed infections in battery-cage experiments, the death rate of unmedicated turkey poults was 33-75%. Weight gains were significantly (P is less than or equal to 0.05) better with 100 ppm monensin than 60 ppm, as were also lesion scores. Under floor-pen conditions there were no significant differences among monensin treatments. Moisture content of the litter was significantly lower in all monensin-medicated pens (40%, compared with 52% moisture in pens of unmedicated controls).