Influence of fiber fermentability on nutrient digestion in the dog

Eight mature dogs (17.2 +/- 0.2 kg) surgically fitted with ileal T-cannulas were used in a replicated 4-X-4 Latin-square-design experiment to evaluate nutrient disappearance at the terminal ileum and through the digestive tra ct. Two fiber types, cellulose, a crystalline, slowly fermented fiber, and pectin, a soluble, rapidly fermented fiber, were fed in different increment s, and the effects on nutrient availability were assessed. Treatments inclu ded 1) 100% cellulose, 2) 56% cellulose and 33% pectin, 3) 66% pectin and 3 3% cellulose, and 4) 100% pectin. Fiber was added at 10% of diet dry matter (DM). Diets were fed at 100% of ME for maintenance and offered at 0730 and 1730 h. All periods were 21 d, which included 3 d of diet transition and 7 d of adaptation. Daily DM intake was 210 +/- 5 g. Total tract and large-in testine DM digestibility increased linearly (P < 0.01) with increased pecti n. These changes in DM digestion were largely the result of changes in fibe r digestion. Fermentation of total dietary fiber in the large intestine wen t from less than zero to 39% of ileal flow (linear, P < 0.01). Total-tract crude-protein digestibility decreased linearly (P < 0.01) with increased pe ctin. This study demonstrated that fiber fermentability significantly affec ts digestion in the dog. Increasing fermentable fiber increased the digesti on of DM and energy. However, increased fiber fermentability inversely affe cts crude protein digestibility. The lower crude-protein digestibility coul d be attributed to larger microbial protein excretion as a result of greate r fermentation of pectin versus cellulose. Nutrition 2000;16:289-295. (C)El sevier Science Inc. 2000.