The rapid growth of aquaculture must be made in a sustainable manner and the use of responsibly sourced raw materials adhering to the circular economy/zero waste concept is a priority. Therefore, the search continues for more environmentally friendly terrestrial plant alternatives, compared to traditionally feed constituents’ fishmeal and fish oils, and current alternatives such as soy. Hempseed, derived from low cannabinoid (THC <0.3 %) industrial hemp, is one promising alternative as the crop is grown within the UK and the cultivation absorbs more CO2 than other commercial cultivars (Visković et al., 2023). Moreover, hempseed is a secondary by-product, further reducing the carbon footprint, because the crops primary use is to produce materials for construction and energy using the plants stalks.
The present study investigated the suitability of a UK produced hemp seed by-product as a protein source for the Scottish Atlantic salmon industry in two stages. The first validated the use of hemp protein (HP) as an ingredient for aquafeeds and assessed its nutritional attributes and digestibility value. This trial included three experimental feeds (a commercial formulation control and two feeds included 30 % of either hempseed meal [HM] or soy protein concentrate [SPC]) containing yttrium as an inert marker, which were fed to Atlantic salmon. At the end of the trial all fish were euthanized, performance and welfare indicators were recorded, and faeces collected for digestibility. No difference in performance or welfare was found, regardless of diet, and hempseed protein digestibility proved to be good with protein and amino acid values close to 100%.
A second longer term trial is ongoing focussing on fish performance and filet quality for the consumer, in addition evaluating effects of the hempseed diet on the gut. Atlantic salmon are being fed either a commercial formulation control or an HM inclusion diet over a ten-week period before euthanasia and collection of samples for chemical, histological and gene expression analysis. Results from this trial will be presented to reveal whether hempseed meal is a viable alternative to SPC in Atlantic salmon diets.
Visković et al., 2023; https://doi.org/10.3390/agronomy13030931