Project Year 2016
Low omega-3 results in pale salmon
Scientists are studying the consequences of low intake of marine omega-3 throughout the entire salmon life cycle. One effect they have identified is paler fillets.
“One reason we are studying this is that we need knowledge about the consequences for the health of the fish and quality of the fillet of further lowering the amount of marine omega- 3 in salmon feed,” says project manager Trine Ytrestøyl, a scientist at Nofima.
She and her colleagues have been conducting experiments with low intake of omega-3 throughout the entire salmon life cycle.
Salmon weighing 40 g were fed 14 different diets until they reached 400 g. From 400 g to 3.5 kg, groups of salmon were given feed with a low content of marine omega-3 (0% and 1%), and then compared with salmon fed with 2.2% omega-3, which is the current level in commercial feed
When the fish reached approximately 1 kg, they were moved from onshore facilities to sea pens. Handling and transport were stressful for the fish.
Three findings were especially interesting: All groups of salmon grew satisfactorily, regardless of the omega-3 level in the feed.
Fewer of the salmon that had been fed with 0% and 1% omega-3 in their feed survived the experimental period than the salmon with 2.2% omega-3 feed. The salmon fed with 0% and 1% omega-3 deposited less astaxanthin, which is a pigment and antioxidant.
In other words, farmed salmon that consume less marine omega-3 are paler. This was also supported by genetic findings.
Nofima scientist Aleksei Krasnov studies gene expression in salmon and has found a correlation between the body’s conversion of astaxanthin and the amount of omega-3 in the diet.
While the use of astaxanthin in salmon feed has increased, the amount retained in the musculature of Norwegian farmed salmon has declined in recent years. This is both inefficient and poses a quality problem, and Nofima scientists are continuing their work to find a solution in a new project.
“We do not yet know how stress affects the colour of the fillet. However, our hypothesis is that when salmon have a low level of marine omega-3 in their diet, they consume more of the stored antioxidant astaxanthin when exposed to stress. We believe this explains the paler fillet colour,” says Ytrestøyl.
IN COOPERATION WITH:
BioMar, NMBU, the Swedish University of Agricultural Sciences, AVS Chile and NIFES
The Research Council of Norway and the Fishery and Aquaculture Industry Research Fund (FHF)