Fiber at moderate inclusion along with the use of feed additives promote gut health by increasing fiber fermentation in the ceca of broilers. In the first study wheat bran was included at 5% into corn- or wheat-SBM based diets and the diets were either supplemented or not with a stimbiotic. Inclusion of WB did not negatively affect performance of broilers, however, wheat bran inclusion decreased nutrient digestibility, but in these diets supplementation with stimbiotic improved digestibility. Oligosaccharide concentration in the ileum and ceca SCFA concentration was decreased with wheat bran or stimbiotic inclusion. In the second study particle size of the wheat bran was reduced and included at 5% into corn-SBM based diets along with stimbiotic. Inclusion of coarse or fine wheat bran increased FCR of starter phase broilers. However, fine wheat bran when supplemented with stimbiotic increased body weight gain in grower phase and overall weight gain. Fine particle size of the wheat bran increased ileal nutrient digestibility and oligosaccharide concentration, and jejunum villi height. There was a decrease in ceca branched chain fatty acid concentration with wheat bran inclusion and stimbiotic supplementation with no effect on straight chain fatty acids. The third study was designed to determine comparison of prebiotic effects from soyhull and wheat bran to prebiotic Xylo oligosaccharides when broilers are challenged with Eimeria. Soyhull was included into diets as low protein soybean meal while WB was added at 5% into corn-soybean meal diets. Soyhull inclusion increased body weight gain and amino acid digestibility before the challenge. During the challenge there were no differences between diets for growth performance, nutrient digestibility, histomorphology, expression of nutrient transporters, and total short chain fatty acids. Challenge reduced the f ileal oligosaccharides levels, but in the non-challenged group concentration was high in regular soybean meal-based diet with less fiber content. In conclusion, fiber inclusion at low levels although increased FCR in young broilers but in older birds when supplemented with feed additives produce beneficial effects by increasing nutrient digestibility and improve overall FCR. The current studies failed to see an increase in short chain fatty acids and oligosaccharide release except for decrease in branched chain fatty acids.