This study evaluated the effects of sodium butyrate (SB) supplementation on small intestine development in broiler chickens. Periodic acid-Schiff (PAS) and immunohistochemistry were used to undertake histological examinations of the duodenum, jejunum, and ileum. Duodenum, jejunum, and ileum histomorphometric data (villus length, crypt depth, goblet cell count), and interleukin-22 (IL-22) and toll-like receptor 8 (TLR8) immuno-stained area tissue coverage were quantified in control and SB supplemented groups. The histological changes inthe SB supplemented group compared to the control group were as follows: There were increased villi lengths, widths, and crypt depths in the small intestine (duodenum, jejunum, and ileum). Increased numbers of goblet cells were observed, especially in the ileum. In addition, the lymphoid tissue within the small intestine was significantly larger (cross-section area=SB 34.8 +/- 0.5m2 vs control 13.2 +/- 0.5m2) and presented with more lymphoid nodules and more diffuse lymphoid tissue in the tunica submucosa, in the SB supplemented group compared to controls. Chickens do not have lymph nodes, therefore the mucosal-associated lymphoid tissue plays a major immunological role. Significant immunohistochemistry expression of IL-22 and TLR8 proteins were observed in the intestinal epithelial layer of the small intestine, which may play a role in protecting against many pathogens and gastrointestinal cancers.