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Archived – BC study compares natural and synthetic pigments
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Which is better for the fish?
Which is better for the bottom line?
Dr. Fiona Cubitt by one of her experimental tanks.
A four-month study conducted through the Centre for Aquaculture and Environmental Research at the University of British Columbia confirms that farmed Chinook salmon derive significant benefits from astaxanthin being added to their feed.
Carotenoids - the family of pigments to which astaxanthin belongs - have previously been identified as enhancing both survival and antioxidant function in fish.
But the study, part of a much larger interdisciplinary project regarding the costs and benefits of a potential organic aquaculture industry for Canada, has yet to have all of its data collated, tabulated and analysed.
As a result, says principal investigator and research associate Dr. Fiona Cubitt, there are only a few preliminary observations which can be made.
One of those, she indicated, is that young chinook salmon typically do not start taking up the pigmentation - whether from a natural source or a synthetic source - until the fish have reached a certain point in their development.
In general, said Cubitt, they don't begin taking it into their flesh until they reach roughly 100 grams.
When they do, said Cubitt, there is a marked difference in color between the larger and smaller fish and between those fed the pigment and those on a control diet with no pigment.
Researchers at the centre started growing nine groups of chinook salmon in separate 4,000-litre outdoor tanks at the facility in June 2006, beginning with fish of about 50 grams. By mid-September, the halfway point in the study, they had grown to an average of 110 grams, and were expected to rise to close to 200 grams by the end of the project.
The program is designed mainly to draw comparisons between natural- and synthetic source astaxanthin as flesh-pigmenting materials for post-smolt chinook, looking at a variety of factors such as industry costs, as well as health and growth benefits. The feed additive is known to provide antioxidant health benefits, but concerns have been raised about the two potential sources for it: from krill in the wild, or from purely synthetic methods of production.
In order to investigate issues associated with organic aquaculture, Cubitt and her associates looked at both synthetically-synthesized astaxanthin and astaxanthin made from natural sources using Phaffia yeast. The fish were sampled for assessment every eight weeks, with data taken on length, weight, growth, pigmentation, and condition factors - using health and welfare indicators.
With the aid of fish-nutritionist Dr. David Higgs, the researchers made up their own feeds with ingredients obtained from companies such as EWOS Canada, mixing the materials, adding fish oil and making their own pellets.
The fish were hand-fed to satiation morning and afternoon, and Cubitt said it was very important to calculate the exact amount of the different kinds of feed each population of fish was eating.
"There have been three of us doing the feeding, so it has been a pretty labour-intensive project," said Cubitt.
Cubitt noted that both astaxanthin and castaxanthin, both of which are used in salmonid aquaculture, are naturally-occurring substances shown to enhance liver and antioxidant function in fish, and conventional fish-farming practice has been to use the two compounds generated from synthetic sources.
Cubitt said though that as fish farmers have increasingly demanded the antioxidants from natural sources, the variety, predictability, cost and quality of those products have also climbed. It has also been suggested that they aren't as effective or predictable as the synthetically-produced pigments - and so may not give the same health benefits. It's that which has led to an investigation to look at the effects of one of the newest natural-source astaxanthin (products) on the market, in a commercial replicated comparison between synthetically- and naturally- produced astaxanthin.
Research team: K.F. Cubitt, A. Chan, J. Mann, J. Henry, S. McKinley and D.A. Higgs. For information contact K.F. Cubitt (Email: kfcubitt@interchange.ubc.ca) or D.A. Higgs (Email: higgsd@dfo-mpo.gc.ca). Submitted by DFO/UBC Centre for Aquaculture and Environmental Research.
Jun.-Nov.'06
