New Method Documents Feed Nutrient Utilization

Aquaculture has experienced enormous growth and plays an\r\nincreasingly important role in providing the world’s protein supply, according\r\nto the Norwegian University of Life Sciences (NMBU).

Sustainable growth in this sector, however, is hampered by\r\nseveral factors, such as access to high-quality feed resources and high feed\r\ncosts. In Norway, NMBU said feed amounts to 2.3 billion euros, or nearly 50% of\r\nthe production costs in salmonid aquaculture, based on data from the Norwegian\r\nDirectorate of Fisheries.

The Foods of\r\nNorway program at NMBU has developed a new method for selecting\r\nsalmon with higher feed efficiency that have the potential to considerably\r\nreduce production costs and the environmental footprint of the aquaculture\r\nindustry, the university said in an announcement.

"With novel indicator traits for feed efficiency, you\r\nget faster-growing fish at a lower cost. In selective breeding, this could be\r\nof great significance," Foods of Norway doctoral student Hanne Dvergedal\r\nsaid.

Norway is the second-largest global exporter of seafood\r\nand the leading exporter of salmonids (Atlantic salmon and rainbow trout). Feed\r\nefficiency is one of the most economically important traits for breeding.

To improve feed efficiency by breeding, feed intake and body\r\ngrowth in individual fish must be measured. This is easily done for body growth\r\nbut very difficult for feed intake, because farmed fish are typically kept in\r\nlarge units and fed communally by dispersing feed into the water, NMBU said.

Dvergedal has been studying feed efficiency in Atlantic\r\nsalmon for the last three years in close collaboration with AquaGen, a breeding\r\ncompany and partner in Foods of Norway. Their results allow for directly\r\nselecting fish with higher feed efficiency without measuring feed intake.

"The results from Hanne’s PhD work are of great\r\ninterest to AquaGen as they may enable us to improve feed efficiency through\r\nbreeding, which fits very well with our strategy to facilitate a responsible\r\nand sustainable development of the aquaculture industry," senior\r\nresearcher Trina Galloway with AquaGen said.

Locating\r\n“bodybuilders”

Due to the practical issues related to measuring feed\r\nintake, growth rate has been the basis for indirectly selecting fish for\r\nimproved feed efficiency since the dawn of the aquaculture industry in Norway\r\nin the 1970s, NMBU said.

The assumption is that growth correlates with feed\r\nutilization. This is generally true, but growth does not explain everything,\r\nthe university said, noting that the fastest-growing fish are not always the\r\nmost efficient. They may also be the most voracious ones, meaning they make\r\npoor use of their feed. In addition to high feed costs, voracious fish also\r\ncontribute to a high level of nitrogen and phosphorus excretion in the sea and\r\nthus have a negative impact on the environment, NMBU said.

Dvergedal has now successfully documented genetic variations\r\nin feed efficiency in Atlantic salmon by measuring the utilization of nutrients\r\nfrom the feed in body tissues, the university reported.

The results show that some fish are indeed more efficient in\r\nconverting nutrients into muscle; they are better “body builders,” NMBU said.

"Growth alone can only explain around 60% of the\r\nvariation in feed efficiency. By adding nutrient metabolism to the picture, we\r\ncan explain almost 80% of the variation. That's a huge leap," Dvergedal\r\nsaid.

AquaGen senior scientist and NMBU associate professor Jørgen\r\nØdegård has been working closely with Dvergedal through the entire study.\r\nØdegård originally proposed finding a way to measure individual feed efficiency\r\nwithout registering feed intake.

"This new method may enable us to identify parent fish\r\nin our breeding population that display a particularly high feed efficiency,\r\nallowing us, in turn, to enhance this trait in the eggs that we sell to our\r\ncustomers," Ødegård said.

Global potential

Enhancing the feed efficiency of farm animals and farmed\r\nfish is one of the main pillars in Foods of Norway’s research, in addition to the\r\ndevelopment of novel, sustainable feeds, NMBU said.

For the global salmon farming industry, the potential for\r\nreducing feed costs, increasing feed resource efficiency and minimizing\r\nenvironmental impact is substantial.

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In 2019-20, Foods of Norway will carry out follow-up studies\r\nto validate the method by using rainbow trout and by performing a large-scale\r\nexperiment with Atlantic salmon in the ocean.

Source : Feedstuff