Abstract
This study evaluated the suitability of canola and flaxseed oils as source of supplemental dietary lipid for fingerlings of rainbow trout. Triplicate groups of the 30 fingerlings were fed twice daily by iso-nitrogenous, and iso-calorific diets for 8 weeks. Experimental diets consisted of 30.2% protein, 18.6 kJ/g energy and 16.6% lipid from fish oil, canola oil, flaxseed oil, 1:1 blends of fish and canola oils, 1:1 blends of fish and flaxseed oils, 1:1 blends of canola and flaxseed oils and 1:1:1 blends of fish, canola and flaxseed oils. Protein and lipid was significantly highest in fish fed the fish and canola oils diet. Condition factor of fingerlings reared on fish oil diet were significantly higher than other treatments. Protein efficiency ratio (PER) was significantly higher in fish fed the flaxseed oil diet and canola and flaxseed oils diet. The results of fatty acid profile revealed that flesh fatty acid composition is effected by dietary fatty acid composition. The highest amounts of HUFA n-3 were detected in fish fed fish oil diet, which was significantly different from other treatments. Present results indicate the fingerlings can be reared on diets in which fish oil has been replaced with canola and flaxseed oils.
Highlights
In the course of just a few decades, fish farming has developed into a highly productive and efficient industry for the production of animal protein for human consumption
Monounsaturated fatty acids (MUFA) concentrations were highest in the canola oil diet (COD) (64.57%), represented mainly as oleic acid (18:1n-9, 59.87%)
The results of the present study suggest that canola and flaxseed oils can be used to replace fish oil without adverse effects on growth performance of rainbow trout fingerlings, as reported in other studies [33,34,35,36]
Summary
In the course of just a few decades, fish farming has developed into a highly productive and efficient industry for the production of animal protein for human consumption. While marine oils are superior in their fatty acid composition, they contain a variety of toxic compounds including polychlorinated dibenzo-p-dioxins (PCDD), polychlorinated dibenzofurans (PCDF) and dioxin-like polychlorinated biphenyls (DL-PCB), the non-ortho and mono-ortho substituted PCBs [2,3,4,5]. These compounds are carcinogenic and immunosuppressive in humans [6,7,8]
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