Étude de l'impact de deux traitements, dont un sans antibiotiques, sur la santé digestive et les populations de Clostridium perfringens dans des élevages de poulets de chair

In view of the increasing problem of antibiotic resistance, the large-scale use of growth promoting antibiotics in food-producing animals is being questioned. The voluntary ban of these compounds since 2006 in Europe, has been associated with a resurgence of necrotic enteritis, an intestinal disease of broiler chickens caused by Clostridium perfringens. Unfortunately, few alternatives are available and the pathogenesis of necrotic enteritis is yet to be fully understood. Surprisingly, there is a paucity of scientific papers on C. perfringens population diversity in broiler chicken flocks as well as on the effects of antimicrobial withdrawal on this bacterial population dynamics.   The current study evaluated the impact of replacing antibiotic growth promoters and anticoccidials, over a 14-month period, on eight commercial broiler chicken farms in Québec. A drug-free rearing protocol, combining essential oil-based products, organic and inorganic acids, anticoccidial vaccination and chick brooding conditions improvement, was used in place of antimicrobials. Zootechnical performances, digestive health parameters and necrotic enteritis occurrence were compared between conventional and drug-free flocks involved in this study. Molecular approaches such as PCR and PFGE were used to monitor the impact of both rearing protocols on C. perfringens populations.  Results show that livability, age at time of slaughter and total condemnations were not affected by the drug-free program. However, the drug-free flocks showed a decrease in mean live weight and in the daily weight gain, while feed conversion ratio was increased for drug-free flocks. Nearly 27% of the drug-free flocks experienced a clinical necrotic enteritis outbreak. Molecular analysis showed that C. perfringens temporal dynamics seems to be little affected by both rearing protocols. For the drug-free flocks, an initially greater genotypic diversity was linked with an increased risk of experiencing necrotic enteritis. On the other hand, recurring outbreaks of the disease in affected flocks caused a significant decrease of this genotypic diversity, as well as an increase in the number of C. perfringens strains carrying multiple virulence genes.   The current study allowed us to better document the economical and scientific aspects of a drug-free broiler chicken production in Québec. A limited number of scientific papers relative to the comparison of the influence of different rearing protocols on C. perfringens populations have been published so far. Results showed that drug-free broiler chicken production in Québec is economically feasible, though impacting the zootechnical and health performances, as well as C. perfringens population temporal dynamics.       Key words : broiler chickens, antibiotics, essential oils, organic acids, anticoccidial vaccination, zootechnical performances, digestive health, necrotic enteritis, Clostridium perfringens, population dynamics

Keyphrases: Clostridium perfringens, Broiler chickens, Antibiotics, Essential oils, Organic acids, Anticoccidial vaccination, Zootechnical performances, Digestive health, Necrotic enteritis, Clostridium perfringens, Population dynamics