Role of vitamins for gastro-intestinal functionality and health of pigs

•Vitamins are absorbed in the small intestine, however for several B-vitamins also in the colon.•Dietary vitamin supplementation influences composition and activity of the intestinal microbiome.•Vitamins control and prevent excessive oxidative and inflammatory reactions in the gut.•Development of alternatives to antibiotics and medical ZnO should integrate the role of vitamins for gastrointestinal functionality.