Effects of dietary xylan on growth performance, digestive enzyme activity and intestinal morphology of juvenile turbot (Scophthalmus maximus L.)

Abstract

A 12-week feeding trial was conducted to evaluate the effects of dietary xylan on growth performance, digestive enzyme activity, and intestinal morphology of juvenile turbot (Scophthalmus maximus L.) with a mean initial body weight of 4.63 ± 0.01 g. Five isonitrogenous and isolipidic diets were formulated to contain 0%, 0.625%, 1.25%, 2.5% and 5% xylan, respectively. The dietary supplementation of 5% xylan significantly decreased (P<0.05) fish feed intake, growth performance and feed utilization, but these parameters were significantly improved (P<0.05) by 1.25% dietary xylan supplement. Similar trends were observed in whole-body protein and lipid contents of experimental fish. The activity of intestinal caseinolytic, trypsin, and intestinal amylase were inversely related to the supplemented dietary xylan (P<0.05). The integrity of the distal intestine was impaired and the length of intestinal epithelium (lIE) significantly declined (P<0.05) when 5% xylan was added to the diet. Results of the present study suggest that dietary xylan affected the growth performance and feed utilization of juvenile turbot, with beneficial effects at an intermediate supplemental level of 1.25% but with adverse effects at higher supplemental levels (5%).