[Possible interesting dietetic effects of lactulose as a feed additive in pig feed]

In reared piglets (n = 10), fattening pigs (n = 20) and sows (n = 8) the effects of lactulose as feed additive on the quality and composition of chyme and faeces were tested to find out potential dietetic advantages of its use. The lactulose concentration in the diets varied between 27-29 g/kg dry matter in piglets and fattening pigs and 55-140 g/kg dry matter in the diet of sows. In piglets and fattening pigs the lactulose intake did not alter the dry matter content and pH in faeces; in spite of the higher concentration lactulose did not result in diarrhea in sows or adult minipigs, there was only a slight decrease in the dry matter content of faeces. In contrast to findings in human beings only traces of lactulose reached the hind gut, although higher lactulose concentrations were measured at the end of the small intestine (in piglets: 10-40 g, in fattening pigs 40-70 g lactulose per kg dry matter of chyme). The oral intake of lactulose did not increase the concentration of lactic acid or volatile fatty acids in the content of the small intestine and did not reduce the pH in the chyme, but in the contents of cecum and colon ascendens higher concentrations of volatile fatty acids were measured (in piglets: significantly higher values, in fattening pigs slightly increased concentrations). In piglets as well as in fattening pigs lactulose resulted in reduced concentrations of ammonia in the content of small and large intestine, further more the concentrations of lipopolysaccharides were increased in the colonal chyme, when pigs ingested the lactulose containing diet. Due to the fact that only small amounts of lactulose reached the hind gut there are doubts, whether lactulose has comparable dietetic effects in pigs as known from human beings (for example laxative effects, forced elimination of bacteria like salmonella). The results obtained here in pigs underline the necessity of experimental studies in the target species (including parameters of digestive physiology, chemical/microbial composition of the chyme) before substances are used and recommended for dietetic purposes in feeding practice. In spite of generally adopted similarity of the alimentary tract in pigs and human beings there are eventually some important differences within the intestine, its digestive capacity or in reactions on ingested substances leading to unexpected results.