Evaluation of strategies to influence the developing microbiota in the gastrointestinal tract of weaning piglets

General concerns regarding the development of cross-resistance of pathogens to antibiotics have led to the ban of in-feed antibiotics in diets for pigs from January 2006 onward. Therefore, researchers are now encouraged to search for alternatives in order to maintain animal health and performance and prevent piglets from post-weaning disorders, thereby production losses for farmers. One of the main purposes is to understand the complex changes that occur in the intestinal tract of piglets due to the weaning process and to develop strategies based on these findings that would help to keep a stable, well adapted microbial ecosystem, capable of preventing overgrowth of disease-causing pathogens. The porcine intestinal tract harbours a highly complex and diverse microbiota that has a profound effect on animal health: it provides the host with nutrients from fermentation processes, produces essential nutrients such as vitamins, contributes to gut maturation, formation of intestinal barrier function, the development of the immune system and even modulates transcriptional regulation. Although knowledge of these complex interactions is limited, novel molecular methods now beginning to provide a deeper insight into this relationship. Approaches targeting the 16S rRNA gene have also expanded our knowledge about the intestinal microbiota in relation to age, weaning and dietary interventions. It is important to note that, although negative effects on intestinal microbiota have been shown in human studies, the prophylactic parenteral administration of antibiotics to newborn piglets is still a common practice among veterinarians with yet unknown effects. On the other hand, numerous commercial products have appeared on the market; some of which have been tested to successfully, demonstrating positive influence on beneficial micoorganisms in weaning piglets. However, their mode of action is often poorly understood. In this context, further studies are necessary in order to find solutions for farmers in the post-antibiotic aera. This review gives a brief overview of recent findings on the establishments of the intestinal microbiota and its contribution to the development of intestinal morphology, intestinal barrier function, immunology and nutrient supply for the host. Furthermore, some possible dietary strategies will be discussed that hold great potential to successfully manipulate this developing ecosystem, especially during the weaning period.