Abstract
The Campylobacter prevalence in free-ranging broiler flocks is usually higher than in conventional flocks, and effective interventions for this production type are needed. This study aimed to investigate the on-farm Campylobacter-reducing effect of feeding three feed additives or a water additive to broilers from hatching to slaughter. Newly hatched Ranger Gold broilers (n = 140) were randomly placed into five cages (n = 28/cage) within a flock of 6,000 broilers. The broilers had access to outdoor areas after day 36. Three groups received one of the following feed additives: 2 % (w/w) Biochar Charcoal Feed Granules for Poultry, 0.125 % Original XPC™ (Saccharomyces cerevisiae fermentate), or 15 % oat hulls. One group received organic acids added to water (Selko®pH E 0.2 % (v/v)), and one group was fed standard feed pellets and water (control). Half of the broilers were sacrificed on day 36 and the rest on day 56 for enumeration and isolation of Campylobacter in cecal contents by culturing. Air samples were collected weekly, and water and boot sock samples were also collected on days 4, 36, and 59 and analyzed for Campylobacter. A selection of the obtained Campylobacter isolates (n = 43) was whole-genome-sequenced. For the three successive flocks tested, all broilers became Campylobacter-positive before access to the outdoors on day 36. Adding biochar in the feed resulted in 0.70 log10 CFU/g lower C. jejuni than the control group on day 59. The addition of organic acids in water resulted in 0.62 log10 CFU/g lower C. jejuni than the control group on day 36. There was a noticeable difference in dominant sequence types (ST) between day 36 (ST52 and ST475) and day 59 (ST45). STs were genetically similar across rotations, indicating transmission of isolates between successive flocks or from the outdoor environment. High variability was seen between calls for further testing to confirm the demonstrated effect.