Scientists and the aquaculture industry are working together to improve protein digestibility in feed used for commercial fish farming.

The project, funded by Innovation Fund Denmark, includes Aarhus University, University of Copenhagen, Technical University of Denmark, and fish feed producer BioMar.

Improving protein digestibility can improve fish growth, reduce environmental impact and save DKK50 million (US$7.7 million) per year, according to a report.

The project aims to increase protein digestibility by at least 1 percent and protein intake by at least 5 percent. This would mean a reduction of nitrogen excretion to the aquatic environment of at least 9 percent.

The project partners hope to optimize the extrusion process of the feed manufacturing process. The problem for researchers, though, is that there is limited knowledge about what happens to the protein when it is heated and processed under high pressure during the extrusion process.

"The extruder is like a ‘black box,’ as we only have limited knowledge on the chemical reactions and physical processes that take place in it," said Trine Kastrup Dalsgaard, associate professor at Aarhus University.

"We find it important to optimize the process and focus on raw material quality in order to minimize any damage to the protein during the processing of feed to achieve optimum fish feed and ensure high fish farming quality," she said.

 Scientists will map the effects of extrusion on the physical and chemical properties of fish feed protein sources and examine how the changes affect fish growth, metabolism, protein intake and nitrogen excretion. They then will be able to develop extrusion tools for different protein feeds that will optimize the process.