Artificial salmon gut developed to ease cost, time in feed trials

SalmoSim developed an artificial salmon gut as a way to reduce feeding trial costs and examine prebiotic and probiotic efficacy for the salmon industry.

We spoke to Martin Llewellyn, senior lecturer, University of Glasgow, and Raminta Kazlauskaite, graduate student and researcher, University of Glasgow, about their work developing an artificial salmon gut during One: the Alltech Ideas Conference in Lexington, Kentucky last month.

One of the goals of their project is to eventually launch an analysis business using the system to provide information to companies working on feed or in-feed elements for salmon diets.

“One of the ways we thought we might understand the community of microbes living in the gut it was to try and replicate it,”​ said Llewellyn.

“We realized it would be potentially a useful application for industry to have an artificial salmon gut,”​ he told us. The system focuses on salmon in the grow-out phase or when they would be living in sea cages, he added.

The alternate gut could help reduce the cost of feeding trials looking at the use or development of prebiotics and probiotics, he said. “At this stage, we can look at the impact of prebiotics like biomoss, [or] yeast cell wall extract,”​ he added.

“We can look at prebiotic effects what microbial classes does it encourage the growth of? Does it protect against invasions of opportunistic pathogens?”​ Llewellyn said. “We can also look at surviving probiotics – if you eat a probiotic there’s no guarantee it’s going to end up living in the gut compartment that the manufacturer says [but] we can actually screen probiotics and say, ‘Yes, this is going to grow and proliferate.’”​

The system also could be used to develop symbiotic feed additives, which combine both prebiotics and probiotics, he added.

Additionally, the team is now looking to add a way to run feed or ingredient digestibility trials using the system, he said.

“We’re also now developing it to do digestibility,” he said. “This is what a lot of people want, so we should be fairly straight forward we just have to adapt the system to strip out micronutrients.”​

“What we need to do over the next 6 to 12 months is we’ve got a couple of customers and potential customers who will come on board and we’ll trial the service with them,” ​Llewellyn added. “They’re our good news stories – people who’ve used the service and benefited and then at that stage go fully commercial.”​

Developing the artificial salmon​

Work on the artificial fish, SalmoSim, started with an interest in developing a way to better understand the microbial ecology within the salmon and to see if they had a bearing on the energetic phenotype of the fish, said Llewellyn.

“Salmon in the wild have about a three-fold variation in their standard metabolic rate – how fast their metabolic clock ticks over – within the same population,”​ he added.

“Some fish have high metabolic rate, high nutritional command they’re dominant, but when winter comes they’ve got to somehow maintain that demand and they’re not very good at surviving through the hard times,”​ he said. “Other fish, [with a] slower metabolic rate can afford to get by on less food, they can handle a period of anorexia more easily – so what we’re interested in doing was understand what the microbial contribution to those phenotypic traits was.”​

The project was funded initially by the Scottish Aquaculture Innovation Center and some industry members, he said.

The design started by establishing the relevant bacterial communities, and determining where in the intestinal tract they live, said Kazlauskaite.

“Then we measured the physiochemical conditions in them – we measured temperature, pH, dissolved oxygen – we wanted to see what conditions were inside in order to replicate them,”​ she added.

The artificial fish contains a series of bioreactors and took about a year to develop, she said.

The group is in the process of validating the artificial gut’s responses using data from a feeding trial that involved a fishmeal-based diet and a fishmeal free diet, she said.

“We analyze what is happening to these microbial communities and how they change once you switch feed,” ​Kazlauskaite said. “We fed the bioreactors for a certain time on a fishmeal diet and then changed to a fish meal zero diet and then we checked if the trends we see in real salmon are similar to what we see in SalmoSim.”​

Initial results are promising, but the final analysis has not been completed, said Llewellyn.

Feed trials, digestibility and stability ​

The system already has the microbial communities and internal conditions needed for digestibility work, said Llewellyn of the next step for the gut’s development.

“It is essentially simulating the intestinal environment, and so once we’ve stripped out the small molecules we should be able to estimate the impact of different feeds in terms of the digestibility,”​ he added.

It is anticipated that the process would take about six months to add to the current system, said Kazlauskaite.

The process would be able to address questions like which protein source is more readily absorbed or check quality in ingredients gathered from different sources, Llewellyn said.

However, an area of primary interest is in helping reduce the cost of feeding trials, he said.

Feed and research trials with fish using a sea cage can cost about £150,000 (US$190,123) and face delays from testing site availability, he said. 

“People have to understand the incredible costs in feed trials in salmon basically and I think this is why an artificial gut system is essentially a no-brainer.”​

“There are only about 10 testing sites across Europe, approximately, and there are 3,000 salmon farms,” ​he said. “There’s just a queue … and no one’s going to buy your product if it’s not had a sea trial.”​

The SalmoSim is intended to provide a way to prescreen ingredients, said Llewellyn. ​

“Say you had 30 different products you wanted to try – we could triage them down to four, the four best, and then you could take those – the idea is to try and save money,” ​he added.