Nutrients and Energy Digestibility of Microalgal Biomass for Fish Feed Applications

Aquafeed accounts for at least 75–90% of aquaculture’s operating costs. Traditional aquafeed ingredients such as fishmeal, fish oil, and soybean meal are unsustainable; further, their increasing cost necessities developing alternative feed ingredients. Microalgae-based aquafeed is not only environmentally friendly, but it can also be cost-effective with proper optimization. In addition, the nutrition profile of microalgae is similar to that of many fishes. The digestibility of a feed is one of the most important factors to consider in feed formulation. A highly digestible feed can lower production costs, reduce feed waste, and reduce the risk of eutrophication. This review discusses the digestibility of various nutrients such as protein, lipid, carbohydrate, amino acids, and fatty acids (including omega-3 fatty acids), dry matter, and energy of various microalgae in fish. Other commonly used aquafeed ingredients were also compared to microalgae in terms of nutrient and energy digestibility in fish. The intrinsic characteristics of microalgae, biomass pretreatment, and feed preparation methods are all discussed as factors that contribute to the nutrient and energy digestibility of microalgae in fish. Furthermore, methods for increasing the digestibility of microalgal biomass in fish are suggested. Finally, the review concludes with the challenges and prospects of using microalgae as a fish feed in terms of digestibility.

Processing Mixed Mesopelagic Biomass from the North-East Atlantic into Aquafeed Resources; Implication for Food Safety

Aquaculture produces most of the world’s seafood and is a valuable food source for an increasing global population. Low trophic mesopelagic biomasses have the potential to sustainably supplement aquafeed demands for increased seafood production. The present study is a theoretical whole-chain feed and food safety assessment on ingredients from mesopelagic biomass and the resulting farmed fish fed these ingredients, based on analysis of processed mesopelagic biomass. Earlier theoretical estimations have indicated that several undesirable compounds (e.g., dioxins and metals and fluoride) would exceed the legal maximum levels for feed and food safety. Our measurements on processed mesopelagic biomasses show that only fluoride exceeds legal feed safety limits. Due to high levels of fluoride in crustaceans, their catch proportion will dictate the fluoride level in the whole biomass and can be highly variable. Processing factors are established that can be used to estimate the levels of undesirables in mesopelagic aquafeed ingredients from highly variable species biomass catches. Levels of most the studied undesirables (dioxins, PCBs, organochlorine pesticides, brominated flame retardant, metals, metalloids) were generally low compared to aquafeed ingredients based on pelagic fish. Using a feed-to-fillet aquaculture transfer model, the use of mesopelagic processed aquafeed ingredients was estimated to reduce the level of dioxins and PCBs by ~30% in farmed seafood such as Atlantic salmon.