Effects of replacing dietary fish oil with canola oil on growth indices, survival rate and body chemical composition of rainbow trout (Oncorhynchus mykiss) fingerling

This study was conducted to evaluate the effects of replacing dietary fish oil with canola oil on growth indices, survival rate and body chemical composition of rainbow trout (Oncorhynchus mykiss) fingerling. For this purpose, three experimental diets were prepared with the same protein level (40%) and fat levels of 100% )First diet with 10% fish oil, second diet with 100% canola oil and third diet with 50% fish oil and 50% canola oil with three replicates). Then 405 fingerling rainbow trout with an average weight of 11±1 g and a density of 45 in 9 ponds were fed in experimental diets for 8 weeks. Based on the results, the combination of 5% fish oil and 5% canola oil in the ration improved the growth indices including: final weight, Increase Body Weight (BWI), Special Growth Ratio (SGR) and Condition Factor (CF) and showed a significant difference with other treatments and the highest amount was observed in 10% fish oil treatment (p<0.05). However, there was no significant difference between treatments in terms of survival rate and protein, fat, ash and moisture content of fish carcasses (p>0.05). Based on the results of this study, replacing part of canola oil with fish oil (50% fish oil with 50% canola oil) in rainbow trout diet has a positive effect on growth indices and can reduce costs by reducing the length of breeding period.