Impact of camelina-containing diets on hepatic transcript expression of Atlantic cod and Atlantic salmon: functional genomics approaches

Xue, Xi (2014) Impact of camelina-containing diets on hepatic transcript expression of Atlantic cod and Atlantic salmon: functional genomics approaches. Masters thesis, Memorial University of Newfoundland.

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Abstract

The finfish aquaculture industry relies heavily on fish oil (FO) and fish meal (FM), two marine-derived ingredients, for the production of aquafeeds. The demands for FO and FM to meet the expansion of the aquaculture industry will exceed the supply from forage fisheries (e.g. herring, anchovies, capelin) which are at a static phase. Therefore, there is a need to find alternatives such as plant-derived oils and proteins that might replace FO and FM, respectively, in aquafeeds. The products from Camelina sativa, camelina oil (CO) and camelina meal (CM), are currently considered viable options for sustainable aquafeed ingredients. Two feeding experiments were conducted to determine the effectiveness of CO as an alternative to FO in the diets for two economically important aquaculture species: Atlantic cod (Gadus morhua) and Atlantic salmon (Salmo salar). The effect of a low level inclusion of CM combined with CO in the salmon diets was also evaluated. Atlantic cod growth (e.g. weight gain) was significantly reduced by replacing 100% FO with CO (100CO) in the diet after a 13-week feeding trial. In contrast, a 100CO diet did not significantly alter the growth performance of Atlantic salmon after a 16-week feeding trial. However, salmon fed the other three camelina-containing diets [100CO + solventextracted FM (100COSEFM), 100CO + 10% CM (100CO10CM), or 100CO + SEFM + 10CM (100COSEFM10CM)], exhibited significantly lower weight gain or weightspecific growth rate (SGR) compared to control fish. In order to study the effect of replacing FO with CO in diets for farmed Atlantic cod and Atlantic salmon on long chain polyunsaturated fatty acids (LC-PUFA) ii biosynthesis, Atlantic cod fatty acyl elongase (elovl) gene family members were characterized at the cDNA level and QPCR assays for genes involved in LC-PUFA biosynthesis for both species were developed. The QPCR-based transcript expression analyses (Chapters 2 and 3) suggest that low LC-PUFA accompanied with high C18 PUFA in the diet may cause the up-regulation of fatty acyl elongase and desaturase genes, critical for controlling the LC-PUFA biosynthetic pathway, in Atlantic cod (elovl5 and fadsd6) and Atlantic salmon (elovl2, fadsd5 and fadsd6a). In addition, a 44K salmonid microarray was used to study the impact of a camelina-containing diet on salmon liver global gene expression, and a set of microarray-identified camelinaresponsive biomarker genes was validated using QPCR (Chapter 3). These functional genomics studies have contributed significant resources (e.g. cDNA sequences and QPCR assays) to the cod and salmonid research communities, and provide valuable information for the development of novel aquafeeds using camelina products.

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