The possibilities of utilization of canola oil in rainbow trout (Oncorhynchus mykiss) diets

In this study, effects of different levels of dietary canola oil on growth, body proximate composition and fatty acid composition of rainbow trout (Oncorhynchus mykiss) were investigated.Five different experimental diets with equal protein (~47%) and lipid (~17%) content containing 0% (100% fish oil as control diet- group BY100), 25% (group KY25), 50% (group KY50), 75% (group KY75) and 100% (group KY100) canola oil were formulated for rainbow trout with a mean weight of 119±0.17 g and fed for 70 days.In the end of the experiment, wet weight gain, specific growth rate, relative growth rate, feed intake, feed efficiency rate, protein intake, protein efficiency ratio, protein retention, hepatosomatic index and vicerosomatic index were unaffected by diet treatment (p>0.05). However, apparent net protein retention was effected by diet (P<0.05), and accounted as minimum in KY50 (%33.64±1.74) and maximum in BY100 (%41.57±0.46). Carcass composition was significantly different between the initals and the end of the groups (P<0.05).Body compositions of rainbow trout fed with the experimental diets were affected by diet excluding crude ash and the minimum and the maximum moisture, crude protein and crude lipid contents were in KY25 (%73.80±0.13) and in BY100 (%74.43±0. 04), in KY100 (%19.84±0.21) and in BY100 (%21.98±0.09), in KY50 (%3.09±0.37) and in KY75 (%4.42±0.39), respectively (p<0.05). Crude fiber content was increased with increasing canola oil in the experimental diets (%0.08±0.00- %0.19±0.01).Body fatty acid compositions were mirrored fatty acid compositions determined in the experimental diets. The maximal existed fatty acids were palmitic acid (C16:0), oleic acid (C:181?9), linoleic acid (C18:2?6) and docosahexaenoic acid (C22:6?3).The maximum and the minumun mean total Saturated Fatty Acid (SAFA), Mono Unsaturated Fatty Acid (MUFA) and Poly Unsaturated Fatty Acid (PUFA) in the experimental diets were in BY100 diet (%34.12±0.51) and in KY100 diet (%16.25±0.38), in KY100 diet (%49.74±0.35) and in BY100 diet (%26.83±0.47) and in BY100 diet (%38.11±0.69) and in KY100 diet (%34.02±0.12), respectively and differed significantly among all groups (P<0.05). In addition, eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), ?-3 and ?-3/?-6 amounts were maximum in BY100 diet (%9.26±0.30, %16.61±0.83, %20.41±0.82 and %2.51±0.13, respectively) and minimum in KY100 diet (%2.32±0.06, % 5.91±0.11, %12.05±0.24 and %0.61±0.01, respectively) while ?-6 was maximum in KY100 and minumum in BY100 (%19.66±0.13 and %8.15±0.16, respectively) (p<0.05).In rainbow trout fed with the experimental diets, total SAFA, total MUFA and total PUFA in all fatty acid were maximum and minumum in BY100 (%31.56±0.78) and in KY75 (%25.07±0.31), in KY75 (%34.72±1.02) and in BY100 (%29.36±0.70) and in KY100 (%38.53±0.65) and in BY100 (%34.34±0.45), respectively (P>0.05). EPA, DHA, and ?-3/?-6 amounts were maximum in BY100 group (%4.60±0.02, 16.28±0.18 and 1.87±0.07, respectively) and minimum in KY75 group (%2.20±0.01 11.17±0.95 and 0.81±0.05, respectively) (p>0.05). ?-3 was maximum in KY25 group (%18.25±1.09) and minimum in KY75 group (%14.86±0.95) while ?-6 was maximum in KY75 group (%18.66±0.39) and minimum in BY100 group (%9.48±0.21).This study was showed that canola oil can be used about 100% replacement of fish oil without any negative effect on growth, chemical composition and fatty acid composition of rainbow trout.Key Words: Rainbow trout (Oncorhynchus mykiss), canola oil, growth performance, chemical composition, fatty acids.