Salmon farmed on modern feeds contains less of the healthy, long-chain fatty acids (EPA and DHA) than before. Up until the turn of the millennium, farmed salmon were fed fish oil as a replacement for their omega-3 rich natural prey. However, fish oil is now a scarce resource, and more than half of the fat in modern feeds comes from plant oils that are inexpensive, but devoid of long-chain omega-3 fatty acids. How can we increase the omega-3 content of salmon on sustainable feeds?
One option is to breed salmon that are well adapted to the feeds of the future. There is heritable variation in salmon’s ability to build EPA and DHA from shorter omega-3 fatty acids. The DNA sequence of salmon is now well known, allowing rapid characterization of heritable differences in nutrient utilization. A salmon family that appears promising on one feed, may not be the best on another. Therefore, we need to understand the salmon’s body as a system: a functional whole made up of parts that mutually affect, but also depend on, each other. A systems understanding of the interplay between feed and genetic factors will allow a tailoring of fish to feed and vice versa, which is robust to fluctuations in feedstuff availability and pricing.
As a first step towards such a systems understanding, the GenoSysFat project involves two biological experiments. 1) A traditional feeding experiment using high- vs low-omega-3 diets and salmon families that differ in feed utilization. 2) A novel study with pieces of liver kept alive and “fed” in laboratory dishes, studying for each fish how different feeds affect metabolism and gene activity. This allows faster and more detailed exploration of the interplay between genetics and feeds. Results will be interpreted with the help of mathematical models for the biochemical reaction networks, which are well established for other species and will be adapted to salmon based on the newly sequenced salmon genome.