As a result, King Salmon produced 1.4 kilograms of fish protein for every kilogram of fish protein in the diet.
“We wanted the trial to show whether we could use Skretting diets formulated with the MicroBalance concept to have lower fishmeal levels in order to manage diet cost in the face of rising marine protein prices,” reports Mark Preece, General Manager of Aquaculture at New Zealand King Salmon.
“Also, we are always keen to enhance the sustainability of our farming operations — which is important to us as responsible fish farmers as it is increasingly to our customers.”
The trial was run in the experimental sea cage facility at the company’s Ruakaka Seafarm, in New Zealand’s Marlborough Sounds. The dedicated research system contains nine sea pens of 125 cubic metres, each capable of growing about 350 Chinook salmon to harvest size, at commercial densities.
Equal growth and mortality
Three diets were tested: a standard Skretting commercial diet at 30% fishmeal and two experimental diets, both at 8% fishmeal. The diets included animal proteins such as blood meal but one of the two 8% fishmeal diets had lower protein than the commercial diet, as part of a study on the protein requirements of Chinook salmon. It was important to understand the performance of reduced-fishmeal diets under challenging summer conditions, so the trial ran for 80 days from early December 2010 to late February 2011, through the middle of the southern hemisphere summer. Growth and mortality were statistically equal in all three treatments.
Micro-nutrients
“The belief that high fishmeal helps salmon grow well through the summer months has been industry folklore for many years,” comments Ben Wybourne, Skretting’s New Zealand Technical Account Manager.
“While it is possible to make low-fishmeal diets that don’t work well, the results from this trial demonstrate there is no performance hit when using low fishmeal in summer, if the fishmeal is substituted appropriately.”
The key to substituting fishmeal was found when Skretting researchers identified a number of micro-nutrients present in fishmeal that proved to be essential to the fish. Having identified them, they were able to find alternative sources of these micro-nutrients. The main benefit, according to Wybourne, is the flexibility the concept provides.
“We can guarantee the digestible nutrient content of a diet while varying the levels of raw materials over a much wider range, according to their availability and cost.”
Lower fishmeal
“These results in our own stocks, and similar results from other facilities, have given us the confidence to move to lower fishmeal in all our production diets,” concludes Mark Preece.
“We are now using fishmeal levels that enable us to produce 1.4 kilograms of fish protein for every kilogram of fish protein we use in our diets — making us net producers of fish protein by a substantial amount — and at a significant cost saving compared with high-fishmeal diets when fishmeal prices are high.”
| Conor Paul, King Salmon Trial System Technician, at the experimental sea cage facility at Ruakaka Bay |
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