The fish feed must contain about 30 per cent fishmeal in order for the salmon to grow and develop normally. However, because fishmeal is a scarce resource and an expensive ingredient in the salmon feed, producers have been using increasingly larger amounts of vegetable ingredients from agriculture.
Scientists at Fiskeriforskning's department in Bergen have invested a huge amount of time identifying which substances in the fishmeal the salmon rely on, so that nutiritonists can produce a better and more reasonably priced feed.
The research so far shows that a key component is hydroxyproline - an amino acid and a building block in proteins. The tests show that feed with an increased content of hydroxyproline causes the salmon to grow more and faster, and that it is more robust.
Up to now, it was not thought that the level of hydroxyproline limited the growth and development of the fish. However, Senior Scientist Anders Aksnes says that with more hydroxyproline in the feed, the salmon eats more and thier weight increases by 14 per cent, compared with that achieved by using most commercial diets currently available.
Improved fish health
Because the fish grows faster, the production time can be reduced. In addition, the health is strengthened such that there are fewer sores and fin injuries on the fish. The results also indicate that feed with more hydroxyproline causes fewer deformations in the bone structure. Improved fish health means a better quality fish, and thus greater earnings.
"We expect that these improvements together amount to a significant profit for the Norwegian fish farming industry," says Aksnes.
Using fishmeal with more hydroxyproline means that more vegetable products can be used, which are cheaper and found in unlimited quantities. This makes it possible to increase feed production, and thus much more salmon can be produced in the future.
The amount of hydroxyproline in fishmeal can be increased by producing a meal based on fish skin and bones, which are rich in this substance. For the fishing industry, these results are good news, as these fractions are usually seen as poorly paid residual raw materials. This discovery means skin and bone may become a more valuable resource in future.
"This is new basic knowledge about what fishmeal and fish feed contain and how the different biological components affect the growth and health of the fish", says Aksnes.
"This means that we can improve salmon production and can get better economy and increased earnings in the aquaculture industry," he adds.
A patent has been applied for on the use of hydroxyproline in fish feed. Further the results from current investigations will also be published in a scientific article.