Effects of dietary canola oil level on growth, fatty acid composition and osmoregulatory ability of juvenile fall chinook salmon (Oncorhynchus tshawytscha)

Article history: Received 16 August 2007 Received in revised form 16 February 2008 Accepted 26 February 2008 This studyassessed refined canola oil (CO) as a supplemental dietary lipid source for juvenile fall chinook salmon, Oncorhynchus tshawytscha, parr with respect to possible effects on their growth and osmoregulatory performance and body composition. Diets with equal protein (∼57%) and lipid (∼19%) content (dry weight basis) were supplemented with lipid from either anchovy oil (AO) or CO with AO so that CO comprised 0 (0CO), 11% (11CO), 22% (22CO), 33% (33CO), 43% (43CO) or 54% (54CO) of the dietary lipid content. Triplicate groups of juvenile chinook salmonwere fed their prescribed diets for 104 days in freshwater (FW) and 31 days in seawater (SW) after a 4-day transitionperiod. Dietary fatty acid compositions reflected the different proportions of AO and CO in the supplemental lipid. Diet treatment had no effect on fish growth, feed intake, feed efficiency, protein utilization,fishmortality or terminalwhole bodywater and ashpercentages.Whole body lipid percentageswere higher in 11CO and 43CO fish than in 33CO fish and in 11CO fish versus 22CO fish. Whole body protein percentages were highest in 33CO, 43CO and 54CO fish and lowest in 0CO and 22CO fish. Terminal whole body fatty acid compositionswere influenced strongly by the dietary fatty acid compositions. Haematocrit andmuscle water percentageswere not affected consistently and plasmaNa and Cl concentrationswere unaffected by diet treatment in FW or 24-h seawater challenges during FW residency. Also, diet treatment had no effect on the physiological parameters after SW residency. We conclude that dietary treatment had no effect on fish growth performanceunderour experimental conditions. Also, the dietary inclusionof COneither facilitatednor impaired the transferof chinook salmonparr to seawater. Thus, COwas found to be anexcellent and cost-effective sourceof supplemental dietary lipid for culture of juvenile fall chinook salmon during freshwater residency. © 2008 Elsevier B.V. All rights reserved.