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The feed reduced lice numbers per fish by 56% in 23-week commercial trial in Scotland.
The feed reduced lice numbers per fish by 56% in 23-week commercial trial in Scotland.

A new functional feed that has been developed to help protect salmon from lice has been launched in Scotland this week.

Shield, which has been formulated by Skretting, has been shown to have a marked impact on lice numbers, both in in vitro and in full-scale commercial trials.

As Alan Bourhill, Marketing Manager for Skretting, explained to Fish Farming Expert: “A large scale commercial trial in Scotland exceeded our expectations. We fed 7000 tonnes of it to fish at one site over a 23-week period and compared this to a nearby site with a comparable lice challenge.

“It resulted in a 42-day delay to the cages reaching an average of 1 louse per fish; the overall level of lice per fish fell by 56%; and the cages containing the fish fed Shield required one less bath treatment, leading to savings of £46,000.

There are two principle ways, according to Alan, that the formula works.

“Our choice of functional ingredients was made to both improve the fishes’ ability to repel lice – it creates more mucous, reducing settlement rates and increasing the time between treatments – and to make the fish more robust by mounting a stronger response to any lice challenge.”

Indeed, tests in a two-part treatment tank at Skretting’s ARC in Stavanger showed a 19% reduction in louse numbers on the side of the tank which contained fish which has been fed entirely on Shield.

“It’s obviously not a solution to lice but is a valuable part of an integrated pest management strategy which will help to reduce overall lice numbers and we’re confident in the science and research behind the feed,” Alan explains.

“Functional feed uptake is increasing – it’s testament to the increasing sophistication of our nutritional understanding – and we’ve had a lot of interest in the product,” he continues.