In nature, weaning is a gradual process from complete dependence on mother’s milk to independent feeding. In commercial pig husbandry, weaning is an early and abrupt event associated with changes in the physical and social environment of the piglet and a dietary shift from consuming sow’s milk to (solid) animal feed. Piglets are generally weaned between 3-4 weeks of age in commercial practice, a time-point when the host physiology is still developing. As a result of multiple environmental/nutritional/psychological stress factors, weaning is characterized by high incidence of intestinal disturbances with diarrhea and lower growth performance in piglets, commonly referred to as the ‘post-weaning dip’. Familiarizing piglets to solid feed prior to weaning during lactation can, although negligible in terms of energy intake, substantially improve their health and growth performance, through a largely unknown mechanism(s). In early life, the impact of microbiota on intestinal development is considered to be substantial. The intestinal microbiota crucially affects the regulation of host metabolism and innate-adaptive immunity, playing a pivotal role in establishing intestinal homeostasis during early life. In newborns, microbiota can be strongly influenced by environmental factors with impact on intestinal immune functions. In this project, we aim to investigate the consequences of feeding fiber-rich solid feed during early life, focusing on intestinal microbiome colonization, immune maturation and host physiology.