Abstract
An increase in fish consumption, combined with a decrease in wild fish harvest, is driving the aquaculture industry at rapid pace. Today, farmed seafood accounts for about half of all global seafood demand for human consumption. As the aquaculture industry continues to grow, so does the market for aquafeed. Currently, some of the feed ingredients are coming from low-value forage fishes (fish meal) and terrestrial plants. The production of fish meal can’t be increased as it would affect the sustainability and ecosystem of the ocean. Similarly, increasing the production of terrestrial plant-based feed leads to deforestation and increased freshwater use. Hence, alternative and environmentally sustainable sources of feed ingredients need to be developed. Microalgae biomasses represent potential feed source ingredients as the cell metabolites of these microorganisms contain a blend of essential amino acids, healthy triglycerides as fat, vitamins, and pigments. In addition to serving as bulk ingredient in aquafeed, their unique array of bioactive compounds can increase the survivability of farmed species, improve coloration and quality of fillet. Microalgae has the highest areal biomass productivities among photosynthetic organisms, including fodder crops, and thus has a high commercial potential. Also, microalgal production has a low water and arable-land footprint, making microalgal-based feed environmentally sustainable. This review paper will explore the potential of producing microalgae biomass as an ingredient of aquaculture feed.
Highlights
Aquaculture is the fastest-growing segment of the food industry
Microlagae have a well-balanced amino acid profile, obviating the need for high-cost amino acid supplements in the diet (Table 3). Microalgae such as Chlorella, Chlamydomonas, Porphyridium, Isochrysis, and Nannochloropsis are high in methionine, which is often lacking in plant-based ingredients (Wan et al, 2019)
A 69%, 58%, and 46% higher weight gains were achieved in Nile tilapia (Oreochromis niloticus) when it was fed a diet containing 15% Chlorella sp., 14% Defatted Nanno chloropis oculata and Schizochytrium sp., and 10% N. oculata, respectively compared to the control diets (Table 4)
Summary
Aquaculture is the fastest-growing segment of the food industry. Aquaculture market size is estimated to be worth US$ 31.94 billion in 2019 (Marketwatch, 2020). Aquaculture has increased the production of fish that are suitable for a plant-based diet. Fat/lipid sources include fish oil, vegetable oil, soya oil, rapeseed oil, sunflower oil, and algal oil Other ingredients, such as fibre, vita mins, minerals, and amino acids, are minimally required for fish per formance but are essential. Examples of ant-nutritional compounds are tannins, saponins, soluble non-starch polysaccharides This affects the growth of fish and leads to feed waste. Lack of essential amino acids and minerals in plant proteins and animal by-products (Shah et al, 2018). Even though plant-based feed has been shown to support fish growth, it lacks essential amino acids such as methionine, tryptophan, lysine, and threonine. Any alternative feed should have high nutritional contents such as omega-3 fatty acids and high protein content, appropriate amino acid profile, digestibility, and palatability. Not to be subjected to any policy restrictions, such as those imposed for GMOs
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