2011 Poultry Science 90:75–82

ABSTRACT This study investigated the effects of di-etary supplementation with the prebiotics fructo-oligo-saccharide (FOS) and mannan-oligosaccharide (MOS) on the performance, small intestinal microflora, and immune response of broilers. Two hundred forty 1-d-old Ross broiler chickens were randomly assigned to 6 dietary treatment groups: control, avilamycin (6 mg/ kg), 0.25 % FOS, 0.5 % FOS, 0.025 % MOS, and 0.05% MOS. Each treatment was fed to 4 replicates of 10 birds per diet for 4 wk. Except for the 0.5 % FOS group, the overall BW gains of birds treated with avilamy-cin and prebiotics were significantly(P < 0.05) higher than those of the control group. No significant differ-ences were found between the control and supplement-ed groups in overall feed intake, feed conversion, an