August 20, 2018     

                                                              
Scientists at US academia create sustainable aqua feed with marine microalga
 

Scientists at Dartmouth College (US) have developed a more sustainable feed aquaculture by using a marine microalga co-product as a feed ingredient, News-Medical.Net reported.

The product is part of a research - which has been described as a first of its kind - to study the replacement of fishmeal with a co-product in feed developed especially for Nile tilapia.

The Dartmouth team had sought to create an alternate feed as a way to deal with environmental sustainability in connection with the use of aqua feed. Through the research, the scientists studied the effectiveness of replacing fishmeal and fish oil with different types of marine microalgae - excellent sources of essential amino acids, minerals, vitamins, and omega-3 fatty acids.

The Dartmouth team's work replaces fishmeal with Nannochloropsis oculata, a marine microalga co-product rich in both protein and omega-3 fatty acids, including eicosapentaenoic acid, which supports fish growth and quality. The co-products are leftover algae meal, after the oils have been extracted from commercially-grown algae biomass to produce nutraceuticals, chemicals and fuel applications.

The research's findings demonstrate the potential of replacing conventional protein ingredients in tilapia feeds. They also showed that the co-product had higher protein content than the whole cells but had lower digestibility than whole cells. In addition, the co-product revealed the highest digestibility of lysine, an essential amino acid that is often deficient in terrestrial crop-based aqua feed ingredients, as well as the highest eicosapentaenoic acid (EPA) digestibility.

The team had also evaluated several feeds with varying percentages of co-product replacing fishmeal.

When 33% of fishmeal was replaced with the co-product, the Nile tilapia had fish growth and a feed conversion ratio and survival rate similar to those on the reference diet for which fishmeal was 7% of the diet. The team hypothesised that the co-product may need to be enhanced with enzyme(s) to improve nutrient availability and counter the lower digestibility observed in the experiment.

"The possibilities for developing a sustainable approach to aquaculture are exciting. Our society has an opportunity to shift aquafeed's reliance on fish-based ingredients to a fish-free product that is based on marine microalgae, and our findings provide new insight into how we can get there," said lead author, Pallab Sarker, a research assistant professor at Dartmouth.

As part of the Darthmouth team's goal to eliminate aqua feed's dependence on marine fish and terrestrial crop inputs, they are combining Nannochloropsis co-product with other marine microalgae to make aqua feeds more sustainable.

- Dartmouth College / News-Medical.Net