Feasibility of using microalgae grown on digestate as a feed ingredient for aquaculture demonstrated by the latest ALG-AD experiments

A recent report produced by Swansea University researchers has highlighted the benefits of including microalgae, grown using nutrients that would otherwise go to waste, as a fish feed.

Experiments conducted with tilapia – a fish used extensively as a model species for aquaculture research – showed that replacement of the majority of fish meal used in aquafeed with a microalgae substitute is possible, with no detrimental welfare effects on the fish.

Whilst growth rates of the fish fed with the ALG-AD feed were slower, there were no harmful effects on the animals, and the growth rate differences could be linked to the fish getting used to the new feed, supported by analysis of the fish microbiome. Additionally, the ALG-AD feed resulted in a greater microbial diversity, which conveys better immunity for the fish.

Fatty acids within the fish were also significantly improved by using the ALG-AD feed, with an improved ratio of omega-3 to omega-6. A better balance of these two fatty acids is known to provide health benefits and could improve the commercial value of the fish.

Further experiments using the ALG-AD feed as a supplement rather than a replacement showed that within 15 days, weight differences between the two groups had gone, and so this feeding technique, alongside a gradual introduction of new feeds, is recommended for aquaculture production.

These results may be of interest to algae producers, as using digestate to grow microalgae for use as a fish feed ingredient may be more cost-effective than using commercially bought nutrients. In addition, this is interesting for aquaculture businesses, as there may be health benefits to using algae grown on digestate in fish feed, alongside the sustainability benefits of reducing the use of fish meal in feed ingredients.

To find out more, please join us on our upcoming webinar where you can ask questions to the team, and sign up to receive the finalised report.