Interactive effects of protein and carbohydrates on production of microbial metabolites in the large intestine of growing pigs

The study aimed at determining the effect of protein type and indigestible carbohydrates on the concentration of microbial metabolites in the large intestine of pigs. The experiment involved 36 pigs (15 kg initial body weight) divided into six groups, fed cereal-based diets with highly digestible casein (CAS) or potato protein concentrate (PPC) of lower ileal digestibility. Each diet was supplemented with cellulose, raw potato starch or pectin. After 2 weeks of feeding, pigs were sacrificed and samples of caecal and ascending, transverse and descending colon digesta were collected for analyses of microbial metabolites. PPC increased the concentration of ammonia, p-cresol, indole, n-butyrate, isovalerate and most of the amines in comparison with CAS. Pectin reduced the production of p-cresol, indole, phenylethylamine and isovalerate in the large intestine compared with potato starch. Starch and pectin increased mainly the concentration of n-butyrate and n-valerate in the colon compared to cellulose. Interaction affected mainly amines. Feeding PPC diet with potato starch considerably increased putrescine, cadaverine, tyramine and total amines concentrations compared with PPC diets with pectin and cellulose, whereas feeding CAS diet with starch reduced their concentrations. There was also a significant effect of interaction between diet and intestinal segment on microbial metabolites. In conclusion, PPC intensifies proteolysis in the large intestine and also n-butyrate production. Raw starch and pectin similarly increase n-butyrate concentration but pectin inhibits proteolysis more efficiently than starch. The interactive effects of both factors indicate that pectin and cellulose may beneficially affect fermentative processes in case of greater protein flow to the large intestine.