Microalgae to replace fish oil for sustainable fish diets

US researchers found that replacing fish oil with Schizochytrium in Tilapia feed actually improved the feed for the fish and also increased certain healthy compounds in the fish.
Between 1980 and 2010, aquaculture contribution to global fishery output for human consumption rose from nine percent to 47 percent and its use of artificial feeds rose from 50 to 66 percent of production. Responsible expansion of aquafeeds, inter alia, requires finding sustainable alternatives to fishmeal and fish oil ingredients, of which aquaculture is the largest user. Aquaculture feeds currently use over 80% of the world’s fishmeal and fish oil, which are extracted from small ocean-caught fish.
To find suitable alternative to fish oil, a 84-day nutritional feeding experiment with dried whole cells of DHA-rich marine microalgaSchizochytrium sp. (Sc) was carried out to determine the optimum level of fish-oil substitution (partial or complete) for maximum growth of Nile tilapia. When fish oil was fully replaced with Schizochytrium (Sc100 diet), the researchers noticed significantly higher weight gain and protein efficiency ratio (PER), and lower (improved) feed conversion ratio (FCR) and feed intake compared to a control diet containing fish oil (Sc0); and no significant change in SGR and survival rate among all diets. The Sc100 diet had the highest contents of 22:6n3 DHA, led to the highest DHA content in fillets, and consequently led to the highest DHA:EPA ratios in tilapia fillets.
It was therefore concluded that Schizochytrium sp. is a high quality candidate for complete substitution of fish oil in juvenile Nile tilapia feeds, providing an innovative means to formulate and optimise the composition of tilapia juvenile feed while simultaneously raising feed efficiency of tilapia aquaculture and to further develop environmentally and socially sustainable aquafeeds. Results show that replacing fish oil with DHA-rich marine Sc improves the deposition of n3 LC PUFA levels in tilapia fillet. These results support further studies to lowerSchizochytrium production costs and to combine different marine microalgae to replace fish oil and fishmeal into aquafeeds.
Source: PLOS ONE