Histological Adaptations of the Gastrointestinal Tract of Broilers Fed Diets Containing Insoluble Fiber from Rice Hull Meal

These two experiments were aimed to determine the effects of diets containing high levels of insoluble fiber from Rice Hull Meal (RHM) on performance and intestinal histological variables of broilers. In the first experiment, 150 10-day-old Hubbard male broiler chicks were randomly allocatted to three treatments and fed diets containing RHM at 0, 50 and 100 g kg^-1 until 42 days old. Body weight gain was significantly higher (p<0.05) in the 100 g kg^-1 RHM group than the control birds, resulting in a decreasing feed conversion ratio. In the second experiment, 64 14-day-old birds were assigned into 4 groups and fed diets containing RHM at 0, 100, 200 or 300 g kg^-1. Tissue sampling procedures of each group were conducted at 42 days old. There were no considerable differences in carcass characteristics, intestinal weight and length, villus area, crypt depth or mucosa thickness. Increases (p<0.05) in intestinal diameter, gizzard weight and muscular is externa thickness were observed in the dietary RHM groups. In contrast, the villus height and the digesta pH of the crop and gizzard tended to decrease with increasing levels of dietary RHM and significantly declined (p<0.05) in the 200 and 300 g kg^-1 groups. Epithelial cells seem to demonstrate similar histological changes. Nonetheless, segmented filamentous bacteria adhered to the ileal epithelial cells in the dietary RHM groups. In conclusion, the present findings suggest that RHM can be used as a source of insoluble fiber in broiler diets at 100 g kg^-1 to improve performance without any adverse effects on carcass characteristics, gastrointestinal tract and histological variables of the intestinal villi and epithelial cells.