Digestibility and Liver Fatty Acid Composition of Rainbow Trout (Oncorhynchus mykiss) Fed by Graded Levels of Canola Oil

This study was aimed to determined the effects of different concentrations of canola oil (CO) on the digestibility, vicerosomatic index (VSI), hepatosomatic index (HSI) and the contents of fatty acids in the liver of rainbow trout (Oncorhynchus mykiss). Rainbow trouts were fed with the experimental diets for 70 days. The diets were given as triplicate groups of rainbow trout (initial weight of 119 g) to apparent satiation twice in a day. There were not significant differences in digestibility of protein and lipid between the experimental diets. VSI and HSI were not significantly different among the all treatment and between the initals and the end of trials (P>0.05). Liver fatty acid contents of all groups were different from each other. Liver fatty acid analyses showed that EPA and DHA from n -3 HUFA's in the fish fed by the fish oil diet (K) and the initial liver samples, oleic acid (C18:1n-9, OA) and linoleic acid (C18:2n-6, LA) in the fish fed by the canola oil (C-50, C-75, C-100) were higher than in the fish fed by the control diet. Arachidonic acid (C20:4n-6; ARA) were 2.54, 3.15, 4.15, 4.63 and 5.64% in C-75, K, C-100, C-50 groups and initial, respectively. n3/n6 rate was quite high in all groups.