Analysis of factors affecting the bacterial community variations in the gastrointestinal tract of pigs

The gut microbiota plays a fundamental role in the state of health, the performances and the welfare of the host. Different variables can affect the composition of the gut bacterial communities influencing the host-microbiota interplay. The aim of this thesis was to test the effect of some factors that could play a role in shaping the bacterial communities of the porcine gastrointestinal tract. In the first study, the microbiota profile from oxyntic mucosa, pyloric mucosa, gastric groove and luminal content of the stomach was analysed in weaned pigs, testing the hypothesis of the existence of multiple microbial niches in the gastric environment. A different pattern between mucosal and luminal bacterial communities was reported. In the second study, the effect of a long-term formic acid administration was tested on growth performances, on the H+/K+-ATPase presence in the oxyntic mucosa, on the expression of gene markers for inflammatory response in jejunal mucosa, and on jejunal bacterial community structure, in weaners piglets. The overall results suggested an adaptive response to the formic acid administration, and the bacterial community showed a reduction in lactic and butyric acid producing bacteria. In the third study, the piglet’s faecal microbiota rearrangement during the weaning transition was analysed taking into account the potential impact of the host A0 blood group. The weaning shift in bacterial community suggested a role of milk-derived lipids in microbiota shaping, while no effects related to the blood group were reported. These studies contributed to the knowledge on bacterial community shaping in young pigs, focusing the attention on aspects not yet well explored for the porcine gastrointestinal microbiota, such as the role of the gastric environment and of the blood group, and showing the effects of potential adaptation to treatments currently used in the swine industry such as the administration of the organic acids.