Effect of wheat bran fiber and bran particle size on fat and fiber digestibility and gastrointestinal tract measurements in the rat

The effect of wheat bran (AACC hard red) and bran particle size on fat and fiber digestibility and gastrointestinal tract measurements were investigat ed with diets containing 5.7-10.7% dietary fiber. Fifty-six male weanling S prague-Dawley rats were randomly assigned to four diets containing 5% cellu lose (C5); 10.5% cellulose (C10); 21.5% coarse (2 mm) wheat bran (CB); or 2 2.2% fine (0.5 mm) wheat bran (FB) in a six-week study. Dietary fiber diges tibilities were significantly different (P < 0.05) among treatment diets (C B > FB > C5 > C10) but there was no effect in fat digestibility among treat ments. High-fiber diets fed to rats resulted in significantly greater wet a nd dry fecal weights than low-fiber diets. Bran diets resulted in significa ntly higher fecal moisture than cellulose diets. Cecum lengths increased si gnificantly with bran diets compared with cellulose diets. The CB diet resu lted in significantly higher stomach weights than with cellulose diets. Sto machs were heavier and cecal lengths were greater with bran diets than with cellulose diets; however, a high-cellulose diet resulted in increased colo n weight. Except for higher fiber digestibility of coarse bran, bran partic le size had no significant effects. Healthful effects of wheat bran may be associated with gastrointestinal morphology and function. Fecal bulking and decreased intestinal transit time can prevent constipation and may dilute or reduce absorption of toxic or carcinogenic metabolites, thus improving g astrointestinal health and lowering the risk of tumor development and cance r.