Bacterial fermentation affects net mineral flux in the large intestine of pigs fed diets with viscous and fermentable nonstarch polysaccharides.

The impact of colonic fermentation on postileal absorption of Ca, Mg, P, Cu, Fe, Mn, and Zn was investigated in 8 ileally cannulated grower pigs (initial BW = 29.1 ± 1.6 kg) according to a double 4 × 4 Latin square. A semi-purified diet was supplemented with 5.20% low viscous, low fermentable cellulose (CEL), 6.25% high viscous, low fermentable carboxymethylcellulose (CMC), 8.95% low viscous, high fermentable oat beta-glucan (LG), or 9.25% high viscous, high fermentable oat beta-glucan (HG), resulting in 5% actual added nonstarch polysaccharides (NSP) in the diets. Because of the intrinsic mineral content in LG and HG, pigs receiving the LG and HG diets had a greater (P < 0.05) daily intake of Mg, P, Cu, Fe, Mn, and Zn, and also Ca for the HG diet compared with the CEL and CMC diets. Different amounts of minerals reached the large intestine for the 4 diets as indicated by the 60 to 86% less (P < 0.05) ileal flow of Ca, Mg, P, and Fe for CMC compared with CEL and HG. Apparent mineral retention was generally less (P < 0.05) for CEL compared with CMC. Regression analyses indicated that postileal flux of Ca, Cu, and Zn were related (R(2) = 0.24 to 0.99; P < 0.05) to short-chain fatty acid (SCFA) concentrations in feces. Postileal Ca absorption was negatively related (R(2) = 0.24; P < 0.05) to fecal total SCFA concentrations when SCFA concentrations were greater than 95.6 mmol/kg of DM. Furthermore, postileal Zn (R(2) = 0.99; P < 0.001) and Cu secretion (R(2) = 0.94; P < 0.001) decreased with increasing total SCFA concentrations in feces. Additionally, postileal secretion of Fe increased (R(2) = 0.20; P < 0.05) with increasing 16S rRNA gene copies of Enterobacteriaceae in feces, whereas the secretion of Cu decreased (R(2) = 0.25; P < 0.01) with increasing gene copies of Enterobacteriaceae. Overall, the apparent retention of Ca, Mg, and P was 27 to 85% less (P < 0.05) for CEL and HG than for CMC, whereas the apparent retention of Fe, Mn, and Zn was less (P < 0.05) for CEL than for CMC, LG, and HG. In conclusion, these data indicate that the stimulation of fermentation by dietary NSP affects net mineral flux in the large intestine that, in turn, can influence mineral excretion in feces. Additionally, negative effects of CEL on apparent retention may increase the daily requirement for minerals of grower pigs.