Additionally, the weight of small intestine was greater for either probiotic- (3.17) or synbiotic-fed birds (3.11) than the controls (2.89). Furthermore, dietary treatments influenced the histomorphological measurements of small intestinal villi. The addition of either probiotic or synbiotic increased (P < 0.05) the villus height:crypt depth ratio and villus height in both duodenum and ileum. The duodenal crypt depth remained unaffected (P > 0.05). However, the ileal crypt depth was decreased by dietary supplementations compared with control. In conclusion, synbiotic or probiotic displayed a greater efficacy as growth promoters for broilers. Furthermore, the dietary supplementations resulted in an increase in the villus height and crypt depth of intestinal mucosa of broilers. The increase in the villus height and villus height:crypt depth ratio was associated with improvement of growth performance for both synbiotic and probiotic. This indicates that the synbiotic and probiotic can be used as a growth promoter in broiler diets and can improve the gut health. These products show promising effects as alternatives for antibiotics as pressure to eliminate growth-promotant antibiotic use increases.