**5. Conclusion**

Gnotobiotic animals are a very useful model in studying the physiology of the digestive tract. The gnotobiotic model allowed us to carry out systematic examination of the effect of a defined microbial population on postnatal intestinal development. We characterized regional variations in morphological and functional responses of the small intestine. We also identified that morphological and functional responses were affected differently by respective bacterial species, supporting the assumption that postnatal bacterial colonization patterns play an important role in neonatal intestinal development. Very good application of gnotobiotic animals is anticipated in the field of study of mutual interaction of natural microflora and pathogens in the digestive tract, mechanisms of probiotic effects of microorganisms. We can conclude that the development of the intestinal mucosa membrane is in direct junction to breeding conditions. In connection with postnatal differentiation and the development of the small intestine in piglets, currently there is increasingly high interest in the explanation of the important role that can be played by colostrum and by milk containing growth factors, hormones and other bio-active compounds. It is likely that removal of milk will have a profound influence upon the processes regulating the growth of cells in the small intestine, their differentiation and function.
