EFFECTS OF SOYBEAN-CONTAINING DIETS ON THE PROXIMAL AND DISTAL INTESTINE IN ATLANTIC SALMON (SALMO-SALAR) - A MORPHOLOGICAL-STUDY

The morphology of the proximal and distal intestine of Atlantic salmon (Salmo salar) was studied after prolonged feeding with diets containing full-fat soybean meal (FFSB) or soybean protein concentrate (SBPC) and compared with fish fed a standard herring meal (HM) diet. To avoid possible changes due to decreased food intake, dietary inclusions of FFSB and SBPC were chosen at such levels that weight gain, and protein and lipid digestibility values were similar for all three groups. The proximal intestine showed no differences among the groups, except for an increased number of goblet cells in the fish fed SBPC. In the distal intestine, the SBPC group showed no abnormalities and was identical to the HM group. In the FFSB group, the epithelium had an increased number of goblet cells and a marked decrease or even absence of absorptive vacuoles. The microvilli of the enterocytes were shortened, with increased microvillar vesicle formation. These changes may be due to the presence of antinutritional factors in the FFSB diet. The possible role of the various antinutritional factors in soybeans for the development of the intestinal lesions, and their effect on growth and performance are discussed.