AQUAFEED ▶▶▶
Dr Pallab Sarker of the University of California studied the effect of feeding microalgae to tilapia.
It has been found that replacing fishmeal and fish oil with a microal- gae blend improves the performance of tilapia.
be attained. In Norway, there is the potential to cultivate far more mussels than can be absorbed by human food market, and the ‘extra’ mussels can thus be ground into meal that can be fed as a protein ingredient to farmed fish. In terms of how much protein could be provided by mussel meal, IMR benthic resources scientist Øivind Strand says there are estimates that 5000 square km of coast would be needed for 1 million tonnes of mussel production, which is less than 5% of Nor- way’s coast. He and other IMR scientists are using modelling to determine how increased cultivation of mussels might im- pact ocean ecosystems. However, they are optimistic. “The blue mussel is an excellent way to replace what’s left of fish meal in the salmon diet and also a great source of Omega fat- ty acids,” Strand says. “This offers a viable way to produce a protein-and-oil rich aquafeed ingredient without using more land or sea area. If we use green energy to harvest the mus- sels, this feed production would be even more sustainable.” Similarly, bristle worms thrive under conditions in open-cage ocean fish farms, and like mussels, they also have a good Omega fatty acid and protein content. While they could not provide the volume that mussels could, researchers at IMR are looking into how worm populations grow, their feed conver- sion efficiency, potential methods of harvesting and so on. Lock and Strand explain that bristle worms grow well on ob- jects with hard surfaces, but there are some potential har- vesting challenges with these organisms in that they tend to prefer a depth of about 100 m.
Other research Anders Kiessling, a former researcher at IMR and currently an aquaculture nutrition professor at the Norwegian University of Life Sciences, with colleague Torbjörn Lundh at the Swed- ish University of Agricultural Sciences, now lead a multi-na- tional collaborative team evaluating alternative feeds that are already regulated but also some that may be approved in fu- ture. These include food waste processed by insects, forestry debris transformed by fungi, and nutrients from extractive
14 ▶ ALL ABOUT FEED | Volume 29, No. 4, 2021
aquaculture, such as farmed blue mussels and sea squirt. A new fermented locally-farmed fava bean concentrate is also being tested as a replacement for soybean meal. The feeds will be given to rainbow trout in experimental settings and it will also be fed at a commercial farm. They will be tested for taste and more by chefs and through feedback from one of Sweden’s largest retail and restaurant chains. The fish will also undergo metabolomic profiling using NMR technology.
Looking forward In a paper titled ‘Thoughts for the Future of Aquaculture Nu- trition,’ scientists from Australia US and Scotland note that, overall, aquafeed R&D is already focused on nutrients, but they urge an even greater emphasis, including nutrients that are not considered strictly essential, in order for the aquacul- ture sector to make larger advances in feed efficiency. And in a new analysis in the journal Nature, Rosamond Naylor, the William Wrigley Professor of Earth System Science at Stanford University (US) and her colleagues note that while aquacul- ture has made significant strides toward sustainability, more effective oversight measures are needed. They recommend, among other actions, incentives for sustainably-designed aq- uaculture systems, and a ‘food systems approach’ to govern- ance that considers nutrition, equity, justice and environmen- tal outcomes across all operations, on land and at sea.
Dr. Pallab Sarker and his colleagues at the University of Califor- nia Santa Cruz, have recently published a paper in the journal Nature on feed for tilapia containing protein-rich defatted bio- mass of microalgae Nannochloropsis oculata (the oil is extract- ed for human dietary supplements). The feed also contains whole cells of DHA-rich microalgae Schizochytrium sp. as a sub- stitute for fish oil. The scientists found significantly better growth, weight gain, specific growth rate and similar feed con- version ratio compared with the reference fish-oil-and-meal diet. The fish-free feed also yielded similar fillet lipid, DHA and protein content.
PHOTO: DR. PALLAB SARKER
PHOTO: DR. PALLAB SARKER
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