New PhD for Skretting ARC explores interaction between salmonids, sea lice and diet

20 October 2017

Dr Rebecca Heavyside successfully defended her PhD thesis at the University of Aberdeen on Monday 25 September. Her thesis, “Dietary modulation of the interaction between salmonid fish and sea lice (Lepeoptheirus salmonis): effects on host attractiveness, skin mucus and immune response,” explored some possible modes of action for functional microingredients in anti-sea lice feeds.

An ongoing challenge

Sea lice are external parasites that present a serious challenge to the salmon farming industry. They attach themselves to the fish skin and eat the protective mucus and skin layers, wounding the fish and suppressing the immune system. Sea lice cause decreased fish quality and growth, increased husbandry and treatment costs, secondary infections, stress and fish losses.

“Several factors have led to the exploration of functional feeds against sea lice, including the growing understanding of the link between diet and immunity and the need for a more integrated pest management approach,” says Heavyside. “Led by growing sea lice resistance to traditional pharmaceuticals and a desire for more natural and sustainable remedies, the feed industry has been exploring the use of natural functional feed ingredients as control mechanisms against these pests.”

Novel techniques

Through the course of her research, Dr Heavyside developed a novel in vitro behavioural bioassay to monitor and assess sea lice activity when exposed to a number of substances. The results stimulated further in vivo studies to determine if the same results could be observed when the substances were added to fish diets. In addition, mucus biochemistry was assessed and distinctions made between different salmonid species.

The final phase of the research explored the impacts of functional diets on the immune system by examining the expression of several key genes. “We want to understand and optimise how microingredients modulate the immune system of salmon to strengthen their natural defences and counteract the effects of the sea lice,” explains Heavyside.

Functional feeds are the future

The results generated by Dr Heavyside’s research indicate that more sustainable and natural functional feeds can be developed as a method of sea lice control in salmonid aquaculture as part of a wider integrated pest management approach. “There is still a lot of work to be done and but with growing interest in natural microingredients and new ingredients constantly becoming available, I’m sure we will continue to develop products to support the farming industry in tackling sea lice.”

Dr Heavyside began her PhD in 2013. The research has been completed in collaboration with Skretting ARC and the University of Aberdeen, with support from the Research Council of Norway.

Dr Heavyside is from England, and has held the position of junior researcher in the health department at Skretting ARC in Stavanger for 4 years.

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