Box and whisker plots of the villus width and height and intestinal goblet cell number of rainbow trout, O. mykiss, fingerlings fed the control diet (commercial diet, Aller Futura; Aller Aqua, Christiansfeld, Denmark) or probiotic diet (commercial diet containing 2 × 104 cfu/g of B. cereus var. toyoi). Measurements of total goblet cell number (full and empty) and villi height were based on the analysis of 8 randomly chosen fields from the intestinal mucosa of 12 fish per diet (3 replicate pens/diet). The asterisk denotes that means for the control and probiotic diets differ (P < 0.01). Solid and dashed lines represent the median and mean values for each set of samples, respectively, whereas dots represent the outliers.