To meet the growing demand for feed ingredients in aquaculture, there is a need to explore alternative and sustainable feed sources. Feathers and grass are low value products from the green sector that are available in many European countries. Both raw materials, however, have poor a digestibility and cannot be directly digested by fish. Many lower trophic organisms on the other hand , such as many gammarid shrimp species that typically feed on dead organic material with poor nutritional value, are known to thrive on low digestible feeds. G ammarids also have suitable protein and fatty acid profiles for fish feed and comprise a natural part of the diet of a wide selection of fish species in nature.
To investigate the feasibility of turning side streams from the green sector (grass pulp and feathers) into raw materials for aquafeeds by secondary bioproduction of low trophic organisms , multiple feeding experiments have been conducted in the project BlueGreenFeed. In one small-scale feeding experiment, juvenile gammarids were fed with four different feeds (feathers , grass pulp , a more digestible mixture of feathers and grass pulp , and sugar kelp as a positive control) for 22 days. For each treatment, the experiment was run in triplicates, with 30 individuals per beaker. Data on growth and survival was recorded , and the chemical composition of both the gammarids and the feeds will be analysed.
Initial results from the feeding experiment showed no significant differences in survival rate between treatments. In terms of the specific growth rate (% SGR), the gammarids fed with kelp and the more digestible mixture of grass pulp and feathers showed a significantly higher growth rate than those fed exclusively with feathers. These results suggest that there is a higher potential for gammarids to grow on and bio-convert pre- processed feathers and grass with both increased digestibility and bioavailability, compared to the same feed stock when untreated. Data on the effect of the feed on the biochemical composition of the gammarids is in progress and will be presented at the conference.