Feeding of neonates with artificial milk formulas delays the maturation of the gastrointestinal mucosa. Na-butyrate has a complex trophic effect on the gastrointestinal epithelium in adults. The present study aimed to determine the effect of milk formula supplementation with Na-butyrate on the gut mucosa in neonatal piglets. Sixteen 3 day old piglets were randomly divided into two groups: control (C, n = 8), and Na-butyrate (B, n = 8). Animals were feed for 7 days with artificial milk formula alone (C) or supplemented with Na-butyrate (B). At the 10(th) day of life the piglets were sacrificed and whole thickness samples of the upper gut were taken for analyses. Administration of Na-butyrate led to significant increase in daily body weight gain as compared to control. In the duodenum, the villi length and mucosa thickness were reduced, however, in the distal jejunum and ileum, the crypt depth, villi length and mucosa thickness were increased in Na-butyrate supplemented piglets as compared to control. Supplementation with Na-butyrate did not affect the intestinal brush border enzyme activities but increased plasma pancreatic polypeptide and cholecystokinin concentrations. These results suggest that supplementation with Na-butyrate may enhance the development of jejunal and ileal mucosa in formula-fed piglets.