Pig - Social Stress - Gastrointestinal Biomarkers

Understanding the relationships between social stress and the gastrointestinal microbiota, and how they influence host health and performance is expected to have many scientific and commercial implementations in different species, including identification and improvement of challenges to animal welfare and health. In particular, the study of the stress impact on the gastrointestinal microbiota of pigs may be of interest as a model for human health. A porcine stress model based on repeated regrouping and reduced space allowance during the last 4 weeks of the finishing period was used to identify stress-induced changes in the gut microbiome composition on 19 stressed compared to 19 control pigs. The V4 region of the 16S rRNA sequences from microbial DNA sampled in the caecum, colon and feces, was amplified and then Illumina sequenced using MiSeq v2 250PE. The application of the porcine stress model resulted in a significant increase in salivary cortisol concentration. The applied social stress resulted in 32 bacteria being either enriched (13) or depleted (19) in the intestine and feces. Our trial revealed that the opportunistic pathogens Treponema and Clostridium were enriched in colonic and fecal samples from stressed pigs. In contrast, the genera Prevotella, Faecalibacterium, Butyricicoccus, Dialister, Alloprevotella, Megasphaera, and Mitsuokella were depleted. These depleted bacteria are of great interest because they synthesize metabolites [e.g., short-chain fatty acids (SCFA), in particular, butyrate] showing beneficial health benefits due to inhibitory effects on pathogenic bacteria in different animal species. Generally, our results provide further evidence for the microbiota-gut-brain axis as indicated by an increase in cortisol concentration due to social stress regulated by the hypothalamic–pituitary–adrenal axis, and a change in microbiota composition, particularly of bacteria known to be associated with pathogenicity and mental health diseases. Some of the findings are published in Frontiers in Microbiology 2023, https://doi.org/10.3389/fmicb.2023.1197371.