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The complex proteins of fish feed

Fishmeal is a complex protein source that is commonly used in fish feed. A new article published in Animal Feed Science and Technology shows how fishmeal physical and chemical properties influence both the production of fish feed and the physical feed quality. High physical feed quality is one of the salmon farmers’ most important criteria. This new knowledge can help the feed producers to better control their production process and to improve the quality of the feed.

Fishmeal is purchased based on a limited number of specifications. Nofima has now demonstrated that these specifications are inadequate in order to predict the physical quality of the fish feed. This new knowledge may also be applied to plant and other animal-based feed raw materials.

Extrusion technology and bread baking

Salmon feed is currently produced by extrusion technology – a rapid kneading and cooking process at high temperature, which may be compared with preparing dough in your kitchen to bake bread. This process results in a series of physical and chemical changes in the feed raw materials. The quality of the fish feed may be controlled and improved by adding starch and other binding agents, but the proteins in the fishmeal will also contribute to the physical quality of the feed.

Major stress on feed

The physical quality of fish feed has become more important in recent years because the feeding system blows the feed through long pipes from storage bins to the fish cages. This exposes the feed to mechanical stress and may lead to crushing. Crushing of the feed pellets is a problem since the fish cannot eat small particles or dust, and the dust clogs up the feeding system.

“During this project we have documented for the first time that variation in the physical and chemical properties of fishmeal influences both the extrusion process and the physical quality of the feed,” says Project Manager and Nofima Senior Scientist Tor Andreas Samuelsen.

The attached document (in Norwegian language only) provides a more detailed description of the various methods utilized in the trials, and how variation in the physical and chemical qualities of the fishmeal influences the fish feed.

Detailed description of the various methods utilized in the trials, and how variation in the physical and chemical properties of the fishmeal influences the fish feed can be found in: Samuelsen, T.A., Mjøs, S.A., Oterhals, Å., 2013. Impact of variability in fishmeal physicochemical properties on the extrusion process, starch gelatinization and pellet durability and hardness. Anim. Feed Sci. Technol. 179, 77-84.

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