Effects of coccidiosis control programs on antibody levels against selected pathogens and serum nitric oxide levels in broiler chickens

SUMMARY In-feed antibiotic growth promoters (AGP) are used in commercial poultry production to improve performance and health. In addition, anticoccidial drugs and vaccines provide protection against avian coccidiosis. However, the combined effects of AGP and anticoccidial control programs on poultry health and immune status have not been adequately addressed. Therefore, we assessed live coccidia vaccination, or feeding with 1 of 6 different diets supplemented with coccidiostatic drugs, in combination with AGP, on antibody levels against selected pathogens and serum nitric oxide (NO) levels in broilers. One-day-old untreated and treated chickens were raised on used litter from a gangrenous dermatitis-endemic farm as a source of microbial infection. Clostridium infection in untreated birds was confirmed by the appearance of bacteria-reactive antibodies, with the early presence of antibodies against chicken anemia virus and infectious bursal disease virus and decreasing levels of NO. Coccidia-vaccinated birds given AGP-supplemented diets, in general, had Clostridium antibody levels equal to those of untreated controls. Similarly, few differences between control and vaccinated groups were evident with seropositivity or NO levels. By contrast, most of the coccidiostat plus AGP treatment groups were associated with decreased Clostridium antibody levels compared not only with the unmedicated group, but also with the coccidia vaccine plus AGP group. We conclude that the use of anticoccidial drugs plus AGP may reduce the incidence of Clostridium infection in poultry compared with coccidia vaccination in the presence of AGP, at least under the experimental test conditions used in this study.