Broiler farming practices using new or re-used bedding, inclusive of free-range, have no impact on Campylobacter levels, species diversity, Campylobacter community profiles and Campylobacter bacteriophages

Abstract

A multi-stage option to address food-safety can be produced by a clearer understanding of Campylobacter's persistence through the broiler production chain, its environmental niche and its interaction with bacteriophages. This study addressed Campylobacter levels, species, genotype, bacteriophage composition/ levels in caeca, litter, soil and carcasses across commercial broiler farming practices to inform on-farm management, including interventions. Broilers were sequentially collected as per company slaughter schedules over two-years from 17 farms, which represented four commercially adopted farming practices, prior to the final bird removal (days 39-53). The practices were conventional full clean-out, conventional litter re-use, free-range-full cleanout and free-range-litter re-use. Caeca, litter and soil collected on-farm, and representative carcases collected at the processing plant, were tested for Campylobacter levels, species dominance and Campylobacter bacteriophages. General community profiling via denaturing gradient gel electrophoresis of the flaA gene was used to establish the population relationships between various farming practices on representative Campylobacter isolates. The farming practice choices did not influence the high caeca Campylobacter levels (log 7.5 to log 8.5 CFU/g), the carcass levels (log 2.5 to log 3.2 CFU/carcass), the C. jejuni/C. coli dominance and the on-farm bacteriophage presence/levels. A principal coordinate analysis of the flaA distribution for farm and litter practices showed strong separation but no obvious farming practice related grouping of Campylobacter. Bacteriophages originated from select farms, were not practice-dependent, and were detected in the environment (litter) only if present in the birds (caeca). This multifaceted study showed no influence of farming practices on on-farm Campylobacter dynamics. The significance of this study means that a unified on-farm risk-management could be adopted irrespective of commercial practice choices to collectively address caeca Campylobacter levels, as well as the potential to include Campylobacter bacteriophage biocontrol. The impact of this study means that there are no constraints in re-using bedding or adopting free-range farming, thus contributing to environmentally sustainable (re-use) and emerging (free-range) broiler farming choices.

Keywords: Campylobacter; bacteriophages; broiler; free-range; litter; re-use.

Figure 1.. Schematic of experimental design.

Figure 2.. Campylobacter levels in caeca across shed sections (C1, C2, C3, and C4) from 24 farm samplings in Year 1 (darker shade) and Year 2 (lighter shade) for conventional full clean-out (CN_FC), conventional re-use (CN_RU), free-range full clean-out (FR_FC) and free-range re-use (FR_RU).

Figure 3.. Campylobacter levels in caeca (log CFU/g), carcass (log CFU/carcass), litter (log CFU/g) and soil (log CFU/g) for conventional full clean-out (CN_FC), conventional re-use (CN_RU), free-range full clean-out (FR_FC) and free-range re-use (FR_RU).

Figure 4.. Percentage of C. jejuni and C. coli (Year 1–Year 2) from 17 farms (24 farm samplings, as some sampled in both years), for conventional full clean-out (CN_FC), conventional re-use (CN_RU), free-range full clean-out (FR_FC) and free-range re-use (FR_RU) (total isolates 812).

Figure 5.. Principal Coordinate Analysis of flaA groups across farms. Free-range-re-use (FR_RU), Free-range full cleanout (FR_FC), Conventional Full clean out (CN_FC) and Conventional re-use (CN_RU). (The dotted lines are 95% confidence intervals that group litter practice) (total isolates 757). (Farms are double lettered with year and colour coded for litter practices).

Figure 6.. Principal Coordinate Analysis of Campylobacter species composition across farms. Free-range-re-use (FR_RU), Free-range full cleanout (FR_FC), Conventional Full clean out (CN_FC) and Conventional re-use (CN_RU). (The dotted lines are 95% confidence intervals that group litter practice), (total isolates 757). (Farms are double lettered with year and color coded for litter practices).

Figure 7.. Campylobacter bacteriophage levels (with enrichment) in caeca (log PFU/g) across shed across segments C1, C2, C3, C4 (A), litter (log PFU/g) across segments L1, L2 and soil (log PFU/g), across segments S1, S2 (B), for farms Year 1, Year 2.