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Effect of Anticoccidials and Antibiotics on the Control of Blackhead Disease in Broiler Breeder Pullets

Department of Poultry Science, University of Georgia, Athens, Georgia 30602

Correspondence: J. Hu, E-mail: jhhu{at}arches.uga.edu

Broiler chicks inoculated with both Histomonas and cecal coccidia developed moderately severe blackhead disease. Antibiotics tested at normal feed or water additive levels had little effect on Histomonas lesions or weight gains. Bacitracin at 100, 200, or 300 g/ton reduced liver lesion scores (P < 0.05) but had no other positive effects. Apramycin at 300 ppm in water reduced liver lesion scores (P < 0.05), but did not improve cecal lesions or weight gains. Penicillin (100 ppm), chlortetracycline (100 ppm), tylosin (110 ppm), and sarafloxacin (40 ppm) in water did not improve liver or cecal blackhead lesions. Weight gains were improved relative to infected controls by treating with penicillin, tylosin, or sarafloxacin (P < 0.05).

Five anticoccidials (salinomycin, diclazuril, nicarbazin, roxarsone, and lasalocid) were tested at common use levels in two trials. Results were similar in both trials; liver lesion scores in the nicarbazin treatment were reduced (P < 0.05) compared with controls and other medicated groups, and the number of birds positive for liver lesions was lower (P < 0.05). Otherwise, anticoccidials had no effect on liver or cecal lesion scores or weight gains. Control of coccidiosis by the anticoccidials (as shown by oocyst counts) varied among products but was not correlated with severity of blackhead lesions. These results suggest that the effect of cecal coccidia on susceptibility of chickens to Histomonas meleagridis is not a simple function of mechanical damage to the cecal mucosa.

Key Words: antibiotic • anticoccidial • blackhead disease • Eimeria tenella • feed additive • Histomonas meleagridis