Oilseed crops as sources of omega-3 long-chain polyunsaturated fatty acids for salmon
Dietary intake of the omega-3 long-chain polyunsaturated fatty acids (LC-PUFA), EPA and DHA, through the consumption of oily fish such as salmon, has been linked with improved cardiovascular health and cognitive development. Salmon, like humans, cannot efficiently produce n-3 LC-PUFA, but rather they accumulate them through their diet which, in the case of farmed salmon, means the feed. Aquaculture is currently consuming around 75 % of all fish oil from the sea with salmon farming accounting for over 60 % of this. Rapidly expanding production of salmon has meant that fish oil levels in feeds has declined leading to a 75% reduction in the n-3 LC-PUFA content of current diets. To enable high levels of these fatty acids to be restored in future diets, it has been necessary to seek new sources of n-3 LC-PUFA to supplement salmon diets. To be feasible, alternative sources have to support efficient and low-cost production methods. In this project, Camelina plants were metabolically engineered to accumulate high levels of EPA and DHA in their seeds. Using this novel terrestrial source utilizes existing farming practice and infrastructure and is an efficient and low-cost production alternative. In a series of experiments the modified Camelina oils were fed to Atlantic salmon post-smolts until doubling their weight. The fish were given different challenges to test the effect on fish performance and welfare including a stress test, recovery and immune competence. Fish performance was similar to control groups and no differences were found with welfare, stress resistance or immunological parameters. The content of EPA and DHA in salmon flesh increased to levels similar to that found in fish fed high levels of fish oils. It is concluded that oils from transgenic Camelina, under the conditions of this project, can be used to ensure farmed salmon have high levels of the essential omega-3 fatty acids in their flesh without compromising fish health and welfare.
The project aims to develop and test entirely new de novo sources of the n-3 long-chain polyunsaturated fatty acids (LC-PUFA), EPA and DHA, as ingredients for Atlantic salmon feeds. The project complies with the HAVBRUK programme call in that it aims: to develop new lipid sources rich in EPA and/or DHA for use in salmon feed that are sustainable, safe and cost-effective.
There may be several options for n-3 LC-PUFA production. However, vegetable platforms are practical in that they are highly organised with a well-established infrastructure for the cultivation, harvest, processing, distribution, marketing and utilisation. The production of n-3 LC-PUFA in the transgenic oilseed crop, Camelina sativa has recently been demonstrated by one of the partners. This was obtained by transformation with algal genes encoding the n-3 LC-PUFA biosynthetic pathway. The resulting oils have over 20 % of total fatty acids as n-3 LC-PUFA. These oils represent a real solution to the supply of EPA and DHA for the aquaculture industry that will maintain the nutritional quality and healthy status of farmed salmon. These transgenic oilseeds can be scaled up to commercial volumes in a relatively short time. Furthermore, as simply a modified vegetable oil, the cost of transgenic Camelina oil should not be prohibitive and are undoubtedly far cheaper than the alternatives. Production of the transgenic oilseed crops can expand as required to satisfy demand from all sectors including both aquaculture and direct human consumption in a responsible and sustainable fashion.
The current project will first evaluate the suitability of a current Camelina oil with 18% 18:2n-6 in salmon. Then, based on this information a new transgenic Camelina will be engineered with a lower target level of 18:2n-6 and tested again. Fish from both trials will be extensively examined with regard to growth, feed efficiency, metabolic impacts, health and welfare parameters using molecular, clinical and biochemical tools.