Histological and micro-/macro-morphological evaluation of intestine in sharpsnout seabream (Diplodus puntazzo) fed soybean meal-based diets added with MOS and inulin as prebiotics

The effects of mannanoligosaccharides (MOS) and inulin (INU) inclusion (8 g kg(-1)) in a soybean meal (SBM)-containing diet on histology, macro- and micromorphology of proximal and distal intestine of sharpsnout seabream (Diplodus puntazzo) were evaluated. 144 sharpsnout seabream (100 g average initial body weight) were fed with 4 isolipidic and isoproteic diets. At the end of the experimental period (114 days), four fish per diet were randomly sampled. The partial substitution of fish meal (FM) with SBM affected the intestine histology and macromorphology of sharpsnout seabream and modified the enterocyte parameters. The addition of prebiotics has not produced positive effects, leading in some cases to a worsening, especially for INU diet that markedly altered the intestine histology. The micromorphological values were in both proximal and distal intestines significantly affected by the diet: in proximal tract, the nucleus was closer to the apex of the enterocyte in soy-fed fish (SBM, IMU, MOS diets), while fish fed with MOS diet showed the lowest value of enterocyte height, significantly different from the FM diet. In distal tract of intestine, fish fed with FM diet showed the highest value for all considered parameters, while MOS diet resulted in the lowest enterocyte height and supranucleus height among the four diets. SBM-containing diets (SBM, IMU, MOS) resulted in lower values than FM diet for the features of enterocyte nucleus. Microvilli height was not affected by the diet in both proximal and distal tracts. In conclusion in this study, the partial substitution of FM with SBM (40 % on protein basis) induced inflammatory reaction of the gut in sharpsnout seabream, evidenced by histological analysis and changes in morphometric characters of villi and enterocytes, not amended by the addition of MOS and even worsened in the case of inulin.