AN OIL CONTAINING EPA AND DHA FROM TRANSGENIC Camelina sativa TO REPLACE MARINE FISH OIL IN FEEDS FOR ATLANTIC SALMON (Salmo salar): EFFECTS ON INTESTINAL TRANSCRIPTOME

Introduction

De novo sources of omega 3 (n-3) long chain polyunsaturated fatty acids (LC-PUFA) are required as alternative to fish oil (FO) in aquafeeds in order to maintain adequate levels of the beneficial fatty acids eicosapentaenoic and docosahexaenoic acids (EPA and DHA, respectively). Recently, oils derived from transgenic Camelina sativa crops containing high levels of EPA or EPA together with DHA were investigated in Atlantic salmon (Salmo salar) in feeds containing relatively high levels of fish meal (FM) and with a focus on liver metabolism (Betancor et al., 2015a,b). However, intestine is the first tissue to encounter dietary fatty acids and is also a site of potentially significant LC-PUFA biosynthesis in salmonids. The present study investigates the high EPA+DHA oil in feed with lower levels of FM and FO reflecting current commercial formulations to determine the impacts on intestinal transcriptome and health of farmed salmon.

Materials and Methods

Isonitrogenous and isoenergetic diets were formulated to satisfy the nutritional requirements of salmon (NRC, 2011). The diets supplied 45 g.kg^-1 crude protein and 21 g.kg^-1 crude lipid and were manufactured at BioMar Tech-Centre (Brande, Denmark). The diets had the same basal composition with added oil supplied by fish oil (FO), wild-type Camelina oil (WCO) or EPA/DHA-Camelina oil (DCO) and were named accordingly. The fatty acid compositions of the feeds are shown in Table 1. Non-defatted fishmeal was employed as the major protein source to ensure EFA requirements were met. Post-smolts were distributed into seawater tanks (38 fish per tank) and fed the three experimental feeds in triplicate for 12 weeks. Growth performance and fish health were determined along with nutrient and fatty acid compositions. In addition, the metabolic/molecular consequences of this new feed ingredient were assessed by analysis of mid and hindgut gene expression using oligonucleotide microarray.

Results and Discussion

The novel oil derived from a transgenic oilseed crop was a suitable substitute for FO in salmon feed as determined by the good performance data obtained. After 12 weeks of feeding the experimental diets, fish more than doubled their weight, with no differences in fish weight, length or other performance parameter evaluated (Table 2). These results agree with those obtained previously where no differences were observed between fish fed an EPA only oil from transgenic Camelina compared to fish fed either FO or WCO (Betancor et al., 2015a).

As expected, fish flesh reflected dietary fatty acid composition, with DCO-fed fish containing higher n-3 LC-PUFA levels than fish fed WCO or FO (Table 1). The results obtained from the present trial and previous ones (Betancor et al 2015a,b) demonstrate that oils derived from transgenic Camelina sativa are a suitable source of n-3 LC-PUFA for salmonids, promoting growth and supporting fish health as well as maintaining high levels of beneficial fatty acids. Thus, oils extracted from transgenic crops represent a feasible source of n-3 LC-PUFA for aquafeeds and, at the moment, are the only viable option to supply the volumes of EPA and DHA-rich oil at a likely cost that animal production can afford.

Acknowledgments

MBB was funded by a UK Biotechnology and Biological Sciences Research Council (BBSRC) Industrial Partnership Award (BB/J001252/1). The salmon trial was supported by a Research Council of Norway FHF-Havbruk Programme award (project no. 245327).

References

Betancor M.B., M. Sprague, S. Usher, O. Sayanova, P.J. Campbell, J.A. and D.R. Tocher, 2015. A nutritionally-enhanced oil from transgenic Camelina sativa effectively replaces fish oil as a source of eicosapentaenoic acid for fish. Scientific Reports 5, 8104.

Betancor M.B., M. Sprague, O. Sayanova, S. Usher, P.J. Campbell,J.A. Napier, M.J. Caballero, and D.R. Tocher, 2015. Evaluation of a high-EPA oil from transgenic Camelina sativa in feeds for Atlantic salmon (Salmo salar L.): Effects on tissue fatty acid composition, histology and gene expression. Aquaculture 444, 1-12

National Research Council (NRC), 2011. Nutrient requirements of fish and shrimp. The National Academies Press, Washington D.C.