Nutrients and Energy Digestibility of Microalgal Biomass for Fish Feed Applications

Abstract

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.

An overview of microalgae biomass as a sustainable aquaculture feed ingredient: food security and circular economy

“…Protein digestibility of microalgae varies from 50% to 94% in different fish species. Protein digestibility of rainbow trout, Nile tilapia, European seabass, and African catfish has been reported to exceed 80% [ 110 ]. In African catfish and Nile tilapia, bead milling improved N. gaditana protein digestibility by 16 and 17 %, respectively [ 86 ].…”

“…exhibited significantly lower mino acid digestibility than juvenile European seabass. Pretreatment would break down larger proteins into peptides and individual amino acids, which increases amino acid digestibility [ 110 ].…”

“…Microalgal carbohydrates are digestible according to the type and quantity of carbohydrates in biomass, as well as the kind of fish that consumes microalgal carbohydrates [ 160 ]. The carbohydrate digestibility of microalgal species varies between 22% and 83%, depending on fish species [ 110 ]. S. maxima and C. vulgaris were found to have a higher carbohydrate digestibility (greater than 70%) in Nile tilapia [ 86 ].…”

“…Thick-walled microalgae are less digestible than species with thin or no cell walls. Desmodesmus, Nannochloropsis, Haemotococcus and Chlorella , microalgae are with thick cell walls, while I. galbana, Porphyridium cruentum , and D. salina are with thin cell walls [ 85 , 110 , 172 ].…”

The Potential of Marine Microalgae for the Production of Food, Feed, and Fuel (3F)

“…The whole biomass of microalgae or their specific metabolites could be used as aqua and animal feed [115]. Recently, it has been reported that microalgal nutritional compounds are ideal for the diet of cattle, chicken, goats, and pigs for the improvement in meat grade with higher PUFAs, especially EPA and DHA, and amino acids [116].…”