Optimal intestinal development in gilts is a prerequisite for a better farrowing and a higher feed intake in lactation, and these are important facets in improving animal welfare for sows in a high-performance situation. The present study aimed to evaluate the effects of a fiber-rich diet on these topics. Studies with 20 male Topigs castrates and a performance study with 38 female siblings were conducted. Pigs in both of the groups were offered either a control diet (CG) or a high fiber diet (FG) during the second half of the rearing phase (~97 kg BW) until 7 days a.p. At the time of the insemination of the gilts (body weight >170 kg), the castrates were slaughtered and the morphological parameters of the gastrointestinal tract were taken. In the performance study, the feed intake as well as the number and weight of the live and stillborn piglets and the weaning weight of the litters were recorded. The results indicated that the high fiber diet with a greater swelling capacity was beneficial to the development of the gastrointestinal tract (stomach weight CG = 714 g, FG = 812 g, p = 0.007), increased the litter weight (CG =15.9 kg, FG = 20.6 kg, p = 0.045) and resulted in a higher feed intake during lactation overall (CG = 196 kg, FG = 211 kg, p = 0.035).