Growth performance, intestinal histomorphology, body composition, hematological and antioxidant parameters of Oncorhynchus mykiss were not detrimentally affected by replacement of fish meal with concentrated dephenolization cottonseed protein

Protein is the most expensive nutrient in aquafeed. Cottonseed meal can be used as an important source of plant protein in aquafeed because of its low price and high yield. Concentrated dephenolized cottonseed protein (CDCP) is a promising alternative source of fish meal obtained by processing cottonseed meal to remove gossypol. In this study, an 8-week feeding experiment was conducted to evaluate the effects of replacing fishmeal by CDCP on growth performance, intestinal histomorphology, body composition, hematological and antioxidant parameters of Oncorhynchus mykiss. Six isonitrogenous (43 %) and isolipid (14 %) experimental diets were formulated to replace 0% (D1), 10 % (D2), 20 % (D3), 30 % (D4), 40 % (D5), 50 % (D6) of fish meal by a corresponding amount of CDCP. The results indicated that the replacement of 10 %–50 % fish meal by CDCP had no adverse effect on the growth, feed utilization and survival rate of O. mykiss. The whole-body and muscle composition and hematological parameters of O. mykiss have not changed due to the replacement of 10 %–50 % of fish meal by CDCP. No significant pathological changes in the mid-gut was observed among all experimental groups. The length of villus was not affected by the substitution of fish meal with CDCP. There was no significant difference on the activity of SOD and T-AOC in fish fed with different diets. However, the MDA contents of fish fed the D1- D3 diets were significantly higher than that of fish fed the D4-D6 diets. In conclusion, there was no adverse effect on growth performance, intestinal histomorphology, body composition, hematological and antioxidant parameters of O. mykiss by replacing 10 %–50 % fish meal with concentrated dephenolized cottonseed protein. The antioxidant capacity of O. mykiss was improved by replacing 30 %–50 % fish meal with CDCP. CDCP is a suitable protein source for O. mykiss.