Effects of Fish Oil Replacement with Vegetable Oils in Rainbow Trout (Oncorhynchus mykiss) Fingerlings Diet on Growth Performance and Foregut Histology

The present study was performed to elucidate the effects of total replacement of fish oil with vegetable oils on growth performance and foregut histological indices of the rainbow trout. Fishes with average initial weight of 15.10±0.20 g were transferred into 15 (300 L) tanks (50 fishes/tank) and reared for 60 consecutive days using different experimental diets. Kilka fish oil (FO) was fully replaced with different vegetable oil sources including canola oil (CO), safflower oil (SO), linseed oil (LO) and a mixture (CSLO) of CO (40%), SO (30%) and LO (30%) as dietary lipid sources. The samples were fixed at 10% neutral-buffered formalin and paraffin sections were prepared and stained with hematoxylin and eosin and periodic acidSchiff methods. Growth performances in CO and CSLO groups were better than other groups. Moreover, in these groups, the number of goblet cells was decreased; however thickness and height of intestinal folds and thickness of tunica mucosa and tunica sub-mucosa were increased in comparison to FO group. Overall, performance and histological findings did not show any negative effect due to canola and mixed vegetable oils feeding compared to FO group.