AQUAFEED ▶▶▶
The potential of microalgae as fish feed
The price of fishmeal continues to rise due to the depletion of fishmeal resources. There is an urgent need to find alternatives to fish meal and fish oil in compound feeds. Microalgae could be such an alternative.
BY KAREN WILLOUGHBY, CORRESPONDENT M
Soybean meal Wheat meal
icroalgae are increasingly being studied as an alternative to fishmeal in aquafeed production. Their net biomass productivity is higher than that of any other terrestrial
plant or animal. Unlike land-based plants, there is no need for microalgae to grow in fertile land. Further, microalgae can be cultivated using seawater or wastewater. The nu-
trient requirement to grow microalgae is relatively simple as opposed to insects and bacteria. Microalgae have the right blend of protein, lipids, and carbohydrates needed to protect fish health. Studies have evaluated the use of microalgae as feed for various fish species. It has a number of benefits such as pro- moting the growth of tilapia and carp, improving the repro- ductive performance of yellow tail cichlid, and enhancing the immune response of rainbow trout. In one study, 31% higher weight gain was achieved in Atlantic salmon when fed a diet containing 5% of the microalga schizochytrium than with a diet without it. Similarly, 30% higher weight gain in Pacific white shrimp was achieved with a diet con- taining 0.75% tetraselmis suecica compared to a diet lacking it. With microalgae-based diets 69%, 58%, and 46% higher weight gains were achieved in Nile tilapia when fed a diet containing 15% chlorella, 14% nannochloropis oculata and
Table 1 – Nutritional content of alternate feed. Feed ingredient
Schizochytrium Tetraselmis sp.
Chlorella pyrenoidosa Chlorella vulgaris Schizochytrium Spirulina maxima Spirulina platensis Green macroalgae Synechococcus sp.
Black Soldier Fly (Hermetia illucens) Hydrolyzed feather meal Saccharomyces cerevisiae Fish meal
Protein (%) 12.5 27.2 57
51–58 12.5
60–71 55.8
3.2–35.2 63
43.6 84.2 50.1 63 44
12.2
Lipid (%) 40.2 14 2
14–22 40.2 6–7 14.2
0.3–2.8 11
33.1 10.4 1.8 11
2.2 2.9
Carbohydrate (%) 38.9 45.4 26
12–17 38.9
13–16 22.2
15–65 15 _ _
4.6 –
39 69
Source: Nagappan, S. (2021). Potential of microalgae as a sustainable feed ingredient for aquaculture. Journal of Biotechnology, 341, 1-20. doi: 10.1111/bc.111111
14 ▶ ALL ABOUT FEED | Volume 30, No. 5, 2022
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