Applied Research Note: Intervention study using biochar and organic acids for reducing Campylobacter in free-range broilers

Poultry is the main reservoir for Campylobacter , the leading bacterial cause of human diarrheal disease. Limited evidence exists on the effectiveness of feed and water additives in reducing Campylobacter in broilers under field conditions. A previous study found that biochar-supplemented feed and organic acids in water reduced Campylobacter levels in the ceca of broilers, with the effects potentially depending on the treatment duration. This study further evaluated these additives—individually and in combination—in free-range broilers under commercial farm conditions. Environmental samples were also analyzed to understand transmission dynamics. A total of 305 broilers were divided into five groups: control pelleted feed (Ct), mashed feed (Ms), biochar with mashed feed (Bc), organic acids in water (Oa), and biochar with mashed feed plus organic acids in water (BcOa). Feed additives were provided throughout the 59-day rearing period, and organic acids were added to the water for 7 days prior to slaughter. The experiment was repeated across three broiler rotations in 2023 on a Danish farm. All broilers in rotation 2 tested positive for C. jejuni at slaughter, while rotation 1 had none, and rotation 3 had four C. coli -positive broilers. In rotation 2, C. jejuni levels were significantly lower in Ms and BcOa groups compared to Ct. Broilers in Bc and BcOa groups had significantly lower weights. Whole genome sequencing revealed environmental strains genetically identical to those from the previous year, indicating on-farm persistence and the role of outdoor environments in transmission. Variation between rotations limits the interpretation of the effects of the tested additives.