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. Several nutritional studies have been performed to improve piglet health and resilience to infectious diseases during the lactation and post-weaning periods, and to identify alternatives to the use of antibiotics and antimicrobials as growth promoters. In the last decades, pharmacological levels of zinc oxide (ZnO) and copper have frequently been used as nutritional strategies to prevent post-weaning diarrhoea because of their antimicrobial activity. However, the use of ZnO was recently banned by the EU from 2022 because of the risk of promoting Anti-Microbial Resistance (AMR). Beyond their role as essential micronutrients, vitamins share several remarkable activities (antimicrobial, immunological and antioxidative) often referred to amongst many of the non-antibiotic feed additives commonly proposed and used for pigs. However, very little research and scientific emphasis are devoted to vitamin nutrition and its role in the gut function and health of livestock. This review discusses how fat-soluble (A, D, E and K) and water-soluble (B-group and C) vitamins may influence gastrointestinal (GI) functionality in general and with specific importance on the challenges associated with the early life of pig gut health and disease prevention. On the basis of the literature review it is suggested that future research and development of alternative strategies to antibiotics and medicinal ZnO should pay attention to the role of vitamins for GI functionality and health of pigs.