Supplementation of pig diet with algal fibre changes the chemical and physicochemical characteristics of digesta

Seaweed extracts, because of their physicochemical characteristics and pote ntial nutritional value, could provide a new source of dietary fibre. This study investigated changes in seaweed fibres (physicochemical and fermentat ive properties) in different digestive sites and their effects on digesta ( viscosity and hydration properties). Sixteen pigs were adapted to a test di et supplemented with 5% algal fibre (either Palmaria palmata (PP), a poorly viscous soluble xylan; or Eucheuma cottonii (EC), a partly insoluble carra geenan; or Laminaria digitata (LD), a highly viscous soluble alginate) or 5 % cellulose (reference fibre). PP did not modify the characteristics of dig esta and was fermented in the caecum (pH 6.1+/-0.4; short-chain fatty acids measured in digesta, 1409 +/- 691 mu mol g(-1) dry matter). EC and LD were mainly insoluble in the stomach, becoming soluble in the intestine; EC was slightly fermented in the colon, giving a low concentration of short-chain fatty acids (303 +/- 122 mu mol g(-1) dry matter). Supplementation of the diet with alginate (LD) increased 3.5-fold the heal viscosity of digesta an d their hydration capacity in the ileum and colon. Thus the physicochemical properties of pig digesta largely depend on the physicochemical properties of the ingested seaweed fibre, the pH and ionic conditions prevailing in t he gut, and their fermentability. (C) 2000 Society of Chemical Industry.