Effects of fiber on digestibility and transit time in dogs

This study examines effects of variations in fiber content on nutrient assimilation, fecal output, and gastrointestinal transit time in the dog. Four normal Beagles were fed four diets in a randomized block design. The basal diet was a canned, balanced, meat-based dog food (Alpo Trio) to which added 3, 6, and 9% by weight of alpha cellulose (Solka Flok). Food intake and fecal outputs were recorded for 5-day periods. Samples of diets and fecal collections were analyzed for dry matter, nitrogen, fat, carbohydrate and ash; digestibilities were calculated. Transit times were measured by a radiographic marker technique. Fecal weight and water increased linearly; digestibility of dry matter decreased from 90 to 70% and ash from 43 to 32% with added fiber. Responses of protein, carbohydrate and fat were less pronounced but were regular; regressions of their digestibilities on added fiber were significant. Regression estimate of true digestibility for alpha-cellulose was 6%. Intestinal transit time decreased from a mean of 37.4 to 28.7 hours with added fiber. Decreased intestinal time would contribute to depression of fry matter digestibility. Increased fecal water output probably also reflected retention by fiber.