The present study aimed to evaluate immunohistochemical changes of mucin- and serotonin-releasing cells in the small intestine induced by various dietary supplementations in quails. A total of 300 one day old quails were randomly divided into 5 equal groups according to the 5 weeks long supplementation: whereas birds of the group I were fed with basal diet, the others were supplemented with prebiotics/probiotics (1 g/kg food, group 2), with organic acids (4 g/kg food, group 3), with both prebiotics/probiotics and organic acids (same dosages, group 4) or with antibiotic (active form of avilamycin, 10 mg/kg food, group 5). Weight growth and food intake were not modified among groups. Density of goblet cells were markedly increased mainly in ileum in all supplemented groups except for the group 5 and in birds co-treated with prebiotics/probiotics and organic acids, the effect was maximal and extended to duodenum and jejunum whereas in antibiotic treated quails the goblet cells were dramatically depleted. In parallel, the number of intestinal serotonin positive (closed and opened types) cells has significantly declined in all supplemented birds: cell depletion was highest in antibiotic supplemented birds and lowest in those supplemented with only organic acids. Additionally, the villus height / crypt depth ratio was also diminished in ileum from birds receiving antibiotic, prebiotics/probiotics alone or combined to organic acids. These results show that antibiotic and other dietary additives alter differently intestinal morphology and especially density of mucin- and serotonin-releasing cells.