Our recent studies of structure and function of gastrointestinal tract mucosa revealed that the domestification of Sus scrofa corresponds with the significant slowing of the organ development. On top of genetic potential, the nutritional factors (or more precisely - lack of certain biologically active substances in the feed of pregnant sows) are responsible. Moreover, feeding neonates with milk replacers instead of mother's milk further slows down the development. This is manifested by reduced mitotic activity in the crypts and enhanced apoptosis of enterocytes. The negative effects consist of slower replacement of fetal type, vacuolated enterocytes to adult type enterocytes, modified profile of brush border enzymes, alterations in intestinal mucosa barrier, higher susceptibility to infectious agents, and many others. On the other hand, farmers in order to intensify the production, shorten the suckling period imposing the neonatal piglets to be weaned at 3-4 weeks of life and even earlier. Altogether, it makes the weaning disorders one of the most important problems in pig husbandry, and the mortality of piglets in the leading pig-producing countries still reaches 10%. A number of strategies have been developed to counteract the post-weaning problems. One of them is to stimulate the development of the gastrointestinal tract of the neonate by supplementation of the sow diet with certain biologically active substances and plants. The other idea is to speed up the postnatal development of the gut mucosa for example by plant lectins. Lessons from pig studies can be also useful in human nutrition and medicine since the development of porcine gastrointestinal tract shows a great similarity to that of humans.