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. 2022 Oct 8;11(19):3126.
doi: 10.3390/foods11193126.

Symbiotic Husbandry of Chickens and Pigs Does Not Increase Pathogen Transmission Risk

Emma Kaeder  1 , Samart Dorn-In  2 , Manfred Gareis  1 , Karin Schwaiger  2
Affiliations

Symbiotic Husbandry of Chickens and Pigs Does Not Increase Pathogen Transmission Risk

Emma Kaeder et al. Foods. .

Abstract

A symbiotic or mixed animal husbandry (e.g., pigs and chickens) is considered to have a positive effect for animal welfare and sustainable agriculture. On the other hand, a risk of infection and transmission of microorganisms, especially of zoonotic pathogens, between animal species may potentially occur and thus might increase the risk of foodborne illnesses for consumers. To prove these assumptions, two groups of animals and their environmental (soil) samples were investigated in this study. Animals were kept in a free-range system. In the first group, pigs and chickens were reared together (pasture 1), while the other group contained only pigs (pasture 2). During a one-year study, fecal swab samples of 240 pigs and 120 chickens, as well as 120 ground samples, were investigated for the presence of Campylobacter spp., Salmonella spp. and E. coli. Altogether, 438 E. coli and 201 Campylobacter spp. strains were isolated and identified by MALDI-TOF MS. Salmonella spp. was not isolated from any of the sample types. The prevalences of Campylobacter coli and C. jejuni in pigs were 26.7% and 3.3% in pasture 1 and 30.0% and 6.7% in pasture 2, while the prevalences of C. coli and C. jejuni in chickens from pasture 1 were 9.2% and 78.3%, respectively. No correlation between the rearing type (mixed vs. pigs alone) and the prevalence of Campylobacter spp. was observed. All swab samples were positive for E. coli, while the average prevalences in soil samples were 78.3% and 51.7% in pasture 1 and 2, respectively. Results of similarity analysis of the MALDI-TOF MS spectra (for C. coli, C. jejuni and E. coli) and FT-IR spectra (for E. coli) of the same bacterial species showed no recognizable correlations, no matter if strains were isolated from chickens, pig or soil samples or isolated at different sampling periods. The results of the study indicate that the symbiotic husbandry of pigs and chickens neither results in an increased risk of a transmission of Campylobacter spp. or E. coli, nor in a risk of bacterial alteration, as shown by MALDI-TOF MS and FT-IR spectra. In conclusion, the benefits of keeping pigs and chickens together are not diminished by the possible transmission of pathogens.

Keywords: Campylobacter spp.; E. coli; FT-IR; MALDI-TOF MS; animal welfare; free-range rearing system.

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Conflict of interest statement

The authors declare that they have no conflict of interest.

Figures

Figure 1
Figure 1
Schematic layout of the pastures and the soil sampling (1 to 5). Pasture 1: pigs and chickens; pasture 2: pigs alone.
Figure 2
Figure 2
Prevalence of Campylobacter spp. in animal and soil samples from two husbandry types. Pasture 1: pigs and chickens were kept together (mixed husbandry). Pasture 2: pigs alone.
Figure 3
Figure 3
Examples of MALDI-TOF MS mass spectra of C. coli and C. jejuni isolated from chickens and pigs. Arrows indicate peaks that are absent or present in both species.
Figure 4
Figure 4
Prevalence of Escherichia coli in animal and soil samples from two husbandry types. Pasture 1: pigs and chickens were kept together (mixed husbandry). Pasture 2: pigs alone.
Figure 5
Figure 5
Example of a dendrogram of FT-IR spectra obtained from E. coli strains isolated from pigs and chickens kept in pasture 1 (mixed husbandry; third sampling run). The blue line indicates the stable cut-off value of 0.300. A main cluster is in the upper horizontal plane. The right side, highlighted in dark and light gray refers to E. coli strains coming from animals. The abbreviation, for example “EK_EC(K)_1.11_I_11_19” stands for: EK = name of author; EC(K) = E. coli (K = cloacal) 1.11 = Pasture 1, chicken no. 1 (no. 01–10 = pigs, no. 11–20 = chickens); I = first biological replicate; 11_19 = month November and year 2019.
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Grants and funding

This work was funded by the Schweisfurth Foundation (Munich, Germany) and Software AG—Foundation (Darmstadt, Germany).

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