The effect of dipeptide, Lys-Gly, supplemented diets on digestive tract histology in juvenile yellow perch (Perca flavescens)

The aim of the present study was to evaluate the effects of three formulated diets: wheat-gluten-protein-based diets supplemented with Lys-Gly dipeptide (LG) or free lysine and glycine (FL), a control diet without lysine supplementation (C) and commercial starter Bio Oregon (BO) for on the growth and digestive system morphology of yellow perch. After 48 days of experimental feeding, fish fed LG diet showed the highest body mass. Fish fed LG diet showed the highest number of gastrin/cholecystokinin positive cells and the lowest number of CD3-positive cells. The brush border of anterior intestine was the most PepT1 immunopositive in fish fed LG diet, the weakest in fish fed C diet. The largest hepatocytes were observed in fish fed BO, while the smallest in those fed FL diet, the difference being statistically significant. Relative hepatocyte cytoplasm volume occupied by lipids was higher in fish fed BO and FL compared to those fed C and LG. Number of proliferating cell nuclear antigen-positive hepatocyte nuclei did not significantly differ among experimental groups. These results indicate that wheat-gluten-protein-based diets supplemented with dipeptide Lys-Gly (LG) were appropriate for yellow perch.