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Symposium discussed fish feed of the future

Scientists know about several ways to achieve improved utilization of feed resources. These were presented the first part of the International Symposium on Fish Nutrition and Feeding (ISFNF) in Molde in early June.

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Portrettbilde av Sissel Albrektsen
Sissel Albrektsen

Senior Scientist
Tlf: +47 55 50 12 04
sissel.albrektsen@nofima.no

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Portrettbilde av Torbjørn Einar Åsgård
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Portrettbilde av Trine Ytrestøyl
Trine Ytrestøyl

Scientist
Tlf: +47 7140 01 35
trine.ytrestoyl@nofima.no

The introductory speaker Øyvind Fylling-Jensen from Nofima asked rhetorically: “How can we provide food for nine billion people globally in 2050?” The United Nations Food and Agriculture Organisation says that food production should grow by 70 percent so to a large extent more food must come from the sea.

The theme of ISFNF, which gathered 430 scientists from around the world, was “Feeding our food”. The presenters at ISFNF had various approaches about how we can maximise the utilization of the raw materials that are used in feed for farmed fish.

The fish’s own potential

Stéphane Panserat from INRA was an invited keynote speaker and he highlighted the potential that lies in the genes of the fish to achieve optimal utilization of the resources.

It was later illustrated by Fredrik Venold from the Aquaculture Protein Centre (APC), who referred to his trial in USA in which rainbow trout that were bred to tolerate a fish feed without fishmeal and with 19 percent soybean meal, developed less problems with enteritis than rainbow trout which were not bred for this trait.

The intersection between genetics and nutrition may hold good opportunities for increased utilization of nutrients, but this field did not stand out at this year’s symposium.

Which plant oil is best for feed?

Giovanni Turchini from Deakin University in Australia presented what he and his collaboration partners found when they compared seven different plant oils with fish oil in feed. They fed the rainbow trout from juveniles through to fish ready for harvesting as portion size, and replaced 75 percent of the fish oil with the seven different oils.

Turchini says that the oils which are cheap to purchase are seldom the most profitable in terms of the cost per kilo of fish fillet. Palm oil, of which large quantities is used for many farmed fish species, is cheap per kilo but costs the most per kilo of fish fillet that is produced. In practice, this oil is not used in Norwegian salmon feed. Fish oil is the most expensive but is intermediate with respect to the cost of the fish fillet produced. The shelf life of fish oil is also shorter as the fat turns rancid quicker. High oleic sunflower oil is cost-effective and gives an acceptable level of omega-3 in the fillet. Soybean oil, which is frequently used in feed for salmon, is also cheap. However, an uneven relation between omega-3 and omega-6 oils develops in the fillet, which is unfavourable.

Increase deposition of nutrients

Even though salmon are significantly better than livestock species such as pig and chicken when it comes to utilizing the nutrients in the feed, only 26 percent of the omega-3 from the feed remains in the edible part of the salmon. The remainder ends up in by-products or is not retained by the salmon at all, says Trine Ytrestøyl from Nofima. She believes the aquaculture industry should work to ensure that less fat is retained in the salmon’s belly.

The utilization of phosphorus is a similar challenge. Phosphorus is a chemical element and the world’s exploitable reserves will soon be exhausted. Using the phosphorus that is accessible in the best possible manner and producing feed that results in a low discharge of phosphorus into the environment is therefore highly important.

Sissel Albrektsen from Nofima has been involved in the development of a method to release virtually all the phosphorus in fish bone and make it more accessible to salmon. She believes the nutrients in the fish bone are an underutilized resource in feed. In addition to utilizing the phosphorus in fish bone better, she also referred to the fact that the salmon’s utilization of other nutrients increases significantly when there is sufficient phosphorus in the feed. The salmon feed used today may contain less phosphorus that is required for the fish to achieve optimal utilization of the other nutrients.

Suttisak Boonyoung from the Tokyo University of Marine Science and Technology pointed to increased utilization of the raw materials by adding various types of amino acids and enzymes (methionine hydroxy analogue, taurine and phytase) to plant feed for rainbow trout juveniles. These additives resulted in the juveniles growing more rapidly, utilizing more of the nutrients for growth and less of the nutrients from the feed going to waste.

Several scientists presented their findings about how it is possible to get the fish to produce more of the long-chain polyunsaturated fatty acids, omega-3. Based on the research effort that was presented at ISFNF, there is reason to be optimistic that the research will produce results.

High tech raw materials

One challenge with utilizing the resources in a sustainable manner is to use raw materials that may not be consumed by humans. Margareth Øverland from APC explained about how by-products from the production of bioethanol can replace plant raw materials such as soybean and rape in fish feed. Experiments carried out by APC and an American collaboration partner were based on bioethanol from corn. The aim in the future is to utilize by-products from bioethanol production of wood that may not otherwise be utilized as food for human consumption.

Trials involving two genetically modified products, soybean oil and yeast, were also presented at ISFNF, but without sensational results.

Whether the scientists’ paths to better utilization of fish feed make a difference in the future remains to be seen. ISFNF ran from June 4-7 and featured the scientists’ latest findings on themes such as feed resources, nutritional requirements, health, feed technology and food quality and safety.

 Nutrition and feed technology  

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