Hemp by-products as a protein source for Scottish Salmon (FS156)

Project Outcome:

The vulnerability of our food system has highlighted the need to look for alternative ingredients of proximity. Industrial hemp production in the UK is projected to grow in the coming years, therefore generating large amounts of by-products such as hempseed.

The aim of the present proposal was to evaluate the feasibility of hempseed meal as an ingredient for aquafeed in Atlantic salmon. The first step was to fully characterise several products. Hempseed meals could contain up to 46% protein and included high levels of aspartic acid, glutamic acid, phenylalanine, hisitidine and arginine comparable to those of fish meal. Levels of methionine are approximately half to those present in fish meal, similar to soy protein concentrate. Minimum levels of antinutritional factors were found in the meals. The two hempseed meal with the highest protein content (42% and 46%) were used at a 30% inclusion level in digestibility feeds and benchmarked against a highly digestible feed. After two weeks, faeces were obtained and digestibility of the two tested hempseed meal calculated. Both meals proved to be highly digestible, with an overall protein digestibility of the ingredients of 100%. The good digestibility of the test ingredients was also corroborated by in vivo digestibility, using an artificial salmon gut (SalmoSim).

The results confirm that hempseed meal can be a good novel ingredient for Atlantic salmon aquafeeds. Long term trials are now needed to evaluate the impact that commercial inclusions of these ingredients can have on salmon performance and stress resistance.