Digestive parameters and gut microbiota load and composition along the <i>in vivo</i> piglet gastrointestinal tract

The increased attention toward the role of the gut microbiome in health and disease for both animals and humans has fueled the demand for more relevant and accurate research models. In this study, we present an overview of biochemical and microbial parameters measured throughout the digestive tract of ten TopigsNorsvin × German Piétrain piglets to better understand the in vivo dynamics of digestive and fermentative processes in different gastrointestinal segments, as pigs are suggested to be a representative animal model for the human gastrointestinal tract. Our key findings include region-specific and significantly differing (P < 0.001) pH profiles, with the stomach having the lowest pH (3.36 ± 0.72) and the ileum the highest (7.24 ± 0.18). Dry matter content also varied significantly (P < 0.001), with the stomach having the highest (27.8 ± 2.4%) and the duodenum the lowest (10.6 ± 0.7%). The average total transit time was 12 hr and 45 min ± 1 h and 42 min. Enzyme activities (pepsin, trypsin, amylase) showed interindividual differences. Amino acid levels varied among piglets, with total concentrations averaging 7.04 × 102 ± 2.29 × 102 µg mL-1 in the duodenum, 1.19 × 103 ± 2.69 × 102 µg mL-1 in the jejunum and 9.39 × 102 ± 2.54 × 102 µg mL-1 in the ileum. Bile acid concentrations varied strongly between piglets, with high levels in the gall bladder and varying levels throughout the digestive tract. Short-chain fatty acid concentrations increased significantly (P < 0.001) along the digestive tract, with the highest levels in the large intestine. The microbial load increased consistently (P < 0.001) along the digestive tract, with the highest loads in the rectum (6.82 × 1010 ± 2.88 × 1010 cells mL-1). The highest microbial diversity was observed in the lower intestine (i.e., caecum, colon and rectum), with significant shifts in microbial community composition, especially from the ileum to the caecum. This study provides valuable insights into the digestive and microbiological parameters of the porcine gut, confirming the pig's relevance as a model for gastrointestinal research. The findings can inform the development of in vitro or ex vivo models, reducing ethical constraints of animal studies and aiding in the assessment of dietary interventions on gut health.