New case study: hemp by‑products as a sustainable protein source for Scottish salmon

As the aquaculture sector grows, it needs new, sustainable protein sources to reduce its reliance on soy as a key feed ingredient (because of its high carbon footprint). Hempseed has emerged as a promising alternative.

Hemp is fast-growing, improves soil health, and captures large amounts of CO₂. With more than 80 approved varieties in the UK, growers can select cultivars with optimal nutritional profiles for aquafeed. Its seeds are already known to be highly digestible in humans and animals, making hempseed meal an attractive candidate for salmon diets. The commercial partner in this project, Rare Earth Global (REG), has developed a UK-based supply model for hemp protein that fits within existing farm rotations, offering both environmental and economic benefits.

This feasibility study examined whether UK‑produced hempseed meal could work as a protein source for Scottish Atlantic salmon, with a focus on nutritional value, digestibility, and how processing affects ingredient quality. Valued at £55k, the project was funded by Seafood Innovation Fund and SAIC. The partners were the University of Stirling and Rare Earth Global, with additional project support from SalmoSim and Mowi.

REG supplied three types of hempseed meal and one hempseed oil for nutritional analysis at the University of Stirling. Two variants with the highest protein levels were chosen for feeding trials and their composition , including amino acids, fatty acids, minerals, and potential anti‑nutritional factors, was assessed.

A two‑week feeding trial with 360 salmon compared two diets containing 30% hempseed meal against a standard control diet. Digestibility was measured using an inert marker, and intestinal health was also assessed.

Results were positive. Protein digestibility reached 84% and 87% in the two hemp-based diets, with many amino acids showing close to 100% digestibility. These findings were confirmed by an artificial gut trial that assessed nutrient availability. Together, the studies demonstrated that hempseed meal is an excellent, highly digestible ingredient suitable for inclusion in salmon feed.

This project highlighted the potential for a scalable, low‑carbon, locally produced feed ingredient that could support both sustainability and domestic supply chains. REG will proceed with a full R&D programme to optimise production, assess long‑term impacts on fish performance, and scale up to an initial target of 65k tonnes of hemp protein annually for the UK feed market.

The full title of this project is ‘Hemp by-products as a protein source for Scottish salmon’.