Effects of replacing dietary fish oil and fish meal with microbial oil and algal biomass on lipid class, total fatty acid and phospholipid fatty acid composition of Atlantic salmon liver and muscle tissues

Guerra, Nigel Ivan (2022) Effects of replacing dietary fish oil and fish meal with microbial oil and algal biomass on lipid class, total fatty acid and phospholipid fatty acid composition of Atlantic salmon liver and muscle tissues. Masters thesis, Memorial University of Newfoundland.

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Abstract

With the continuous growth of aquaculture comes a growing demand for an alternative lipid source for fish oil (FO) and fish meal (FM) in aquafeeds. Certain microorganisms provide a potential sustainable replacement for FO and FM due to their content of omega-3 (ω3) long-chain polyunsaturated fatty acids, which are essential for the growth and health of fish. Two feeding trials were conducted to determine the effects of replacing FO and FM with oil and biomass from two different microorganism species. The first feeding trial comprised of replacing FO with a microbial oil (MO) derived from a novel strain, Schizochytrium sp. (strain T18), in diets for Atlantic salmon. Four experimental diets were developed: a fish oil control diet (FO), a blend of fish oil/canola oil control diet (FO/CO), a fish oil replacement with low proportions of microbial oil diet (LMO), and a fish oil replacement with high proportions of microbial oil diet (HMO). After 16 weeks of feeding, there were no significant effects on growth parameters across the dietary treatments. Fatty acid profiles reflected the diets with DHA being present in high proportions in the tissues, especially in the cellular membrane. The purpose of the second feeding trial was to reduce FO and replacing FM with algal biomass (AB) derived from Pavlova sp. strain CCMP459 (Pav459) in diets for Atlantic salmon. Three experimental diets were developed: a fish meal control diet (FM), a blend of a fish meal/algal biomass Pav459 diet (FM/AB), and a complete FM replacement with algal biomass Pav459 diet (AB). After 12 weeks of feeding, again, there was no significant effect on growth paraments, and the fatty acid profiles also reflected those of the diets. The DHA was present in high proportions in the tissues for all dietary treatments, especially the cellular membrane. The stable isotope data suggested a direct integration of EPA and DHA and not biosynthesis from its precursor ALA.

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