When the diets of farmed fish are altered, the food we
ingest also changes. For his doctorate, Sverre Ludvig
Seierstad investigated the biological consequences of
exchanging the fish oils commonly used in fish feed with
vegetable oils. What consequences might this have on both
fish and human health? The research project “Fjord
til bord (Fjord to table)” has been a collaboration
between the Norwegian School of Veterinary Science, the
National institute for Nutrition and Seafood Research
(NIFES), Nutreco ARC and Ullevål University Hospital.
The main ingredients of fish feed have traditionally
been of marine origin. For several reasons, including
increased demand for and production of farmed fish, and
climatic considerations, feed ingredients of marine origin
are becoming both scarce and expensive. The fish farming
industry therefore wishes to utilise alternative lipid
(fat) sources in feed used for salmon farming.
Vegetable oils have been shown to stimulate the appetite
and feed intake of fish, and to increase growth rate and
carcase quality. This doctorate investigated some consequences
of the use of these alternative fish oils in the feed
on the health of both fish and humans. Marine oils are
rich in long-chain omega-3 fatty acids (EPA and DHA),
which have been shown to have beneficial effects on heart
and circulatory system disease in man. Seierstad’s
research focussed on the behaviour of marker substances
for heart and blood vessel parameters, and for inflammation,
in both salmon and humans.
The feeding trials with farmed salmon were carried out
at Gildeskål and in Stavanger. Wild salmon, caught
in Namsen (Lilleøen, Namsos), were used as a reference
During his studies, Sverre Seierstad investigated the
development of thickenings in the wall of the cardiac
arteries of Atlantic salmon at different stages of the
fish’s life cycle and showed that the composition
of fats in the feed had no effect on the development of
constrictions in the cardiac arteries of farmed salmon.
In collaboration with Ullevål Hospital, heart patients
with atherosclerosis (disease of the cardiac arteries)
were placed on three different diets, using salmon meat
containing varying amounts of fish oil and vegetable oil.
It was shown that the fat composition of the salmon meat
affected the fatty acid profile of the patients’
blood and that the advantageous marine omega-3 fatty acids
increased markedly in those patients that ate fish fed
on feed containing pure fish oils. It was also shown that
in these patients the levels of marker substances for
heart and vessel disease were much better than in patients
eating fish fed pure rapeseed oil.
Sverre Ludvig Seierstad defended his Dr. Med. Vet. thesis
with the title “The effect on fish and human health
of replacing marine oils by vegetable oils in feeds of
Atlantic salmon”, at the Norwegian School of Veterinary
Science on February 15, 2008.