New research shows that using certain feed ingredients can improve fish gut health, which may impact how they respond to stress. A bolder, more proactive fish may prove better suited for intensive farming and can thus have greater value for the aquaculture industry.
This was one of the main findings in the recently submitted PhD thesis of Alexandra Leeper, investigating the impact of different protein sources for salmon, and how different protein sources in fish feed can affect growth performance and health, but also whether it has implications for the behaviour of the fish.
This change in behaviour may be linked to the effect of the feed on the fish gut microbiome, Alexandra explains.
“Fish fed different protein sources may have different welfare, supporting the theory that health is connected to behaviour, and that we are what we eat”, she says.
The aquaculture industry experience great losses when the fish are put through stressful situations, for instance in their transfer to sea water. Improving their ability to cope with these situations could help meet this challenge.
“There is a lot of behavioural research done related to the survival of fish, and it is interesting to bring this into farming conditions, where the rules of the wild do not apply”, Alexandra says.
Need more alternatives
In one of her experiments, Alexandra investigated the difference in the impact of marine protein and plant protein on the coping style of the fish. This study was the first of its kind and revealed that fish fed fish meal tended to be more proactive and may experience better welfare in intensive farm conditions.
Fish meal has long been a valuable protein source in fish feed, but competitive prices caused the transition to soybean meal and concentrate as partial replacements. However, researchers still seek to find more nutritionally compatible alternative proteins. As part of her research, Alexandra investigated yeast from forestry side streams and insects grown on food waste, both proving to have beneficial properties for the gut health of the fish, up to a certain inclusion level.
Professor Margareth Øverland was Alexandra’s main supervisor at NMBU. She is also the head of Foods of Norway, a centre for research-based innovation at the Norwegian University of Life Sciences (NMBU), which aims to produce sustainable feed ingredients from local resources for livestock and fish. Alexandra’s research, financed by several projects at research and development organisation Matìs in Iceland, offers a very important perspective on the impact of both novel and existing feed resources used in the aquaculture industry, Margareth says.
“We know that we need to expand our view of what can be used as feed ingredients. This should be done through improving our understanding of the resources already available to us, but also the potential of novel resources”, she explains.
Alexandra says that her findings should be explored further, but that they already indicate a potential for value adding knowledge for the aquaculture industry.
“Knowing how to impact the behaviour of fish through feed should affect what we decide to feed them and give us more tools in feed production. This could improve the success of the industry”, she says.
Alexandra Leeper is defending her thesis publicly on 10 December 2021, at 12:15 pm in H 109 at the Department of Animal and Aquacultural Sciences, NMBU.