Investigating the transfer of E. coli through agricultural systems

Kenneth Porter

March 24th, 2017

Here is a quick overview of some work I began at Rothamsted research’s North Wyke farm platform in November:

Intensification of agricultural systems resulting from an increase in demand for food production can lead to unsustainable use of (in)organic fertiliser. For example an increase in on farm livestock numbers will lead to increased volumes of faeces being applied to land either as slurry, manure, or direct deposits from grazing livestock. Following rainfall, mobilisation of pathogens associated with these faeces into the catchment system can impact downstream ecosystem services associated with clean drinking, bathing and shellfish harvesting water.

SCIMAP is a risk based model of diffuse pollution transport which has been optimised for diffuse sediment and nutrient pollution. My trip to the North Wyke farm platform provided an opportunity to test SCIMAP’s consideration of E. coli pollution, an internationally accepted indicator of faecal pollution. SCIMAP uses the critical source area concept whereby sources of pollution are only a problem when they are connected to the stream network. The approach assumes a topographical control on the connection of sources of pollution to the stream network. Therefore we should expect to see increased levels of contamination in the soil of topographical pinch points, points that are disconnected from the stream network but have a large contributing area. Overland flow, and potentially its constituents, will accumulate in these areas. In this study we test this assumption when SCIMAP is applied to E. coli transfer by using SCIMAP to determine the location of topographical pinch points and compare E.coli contamination at these points with non-pinch points.

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This work will contribute to the assessment of SCIMAP as a useful tool for the determination of areas of the landscape that contribute to diffuse faecal pollution providing opportunities for spatial prioritisation of mitigation effort.

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Seaweed and maggots as feed for farmed fish: are there microbiological risks for human consumers?

Isobel Swinscoe

March 31st, 2017

If you were to be asked ‘What do farmed fish in Europe eat?’, your first answer would probably not be insect larvae! And you’d be right. Concerns about overfishing wild catch to feed farmed fish has led to greater inclusion of vegetable ingredients in aquafeed, leading to competition with human food resources. Yet providing an insect diet is established and accepted practice in fish farms throughout Africa, Asia and South America. Insects form part of the natural diet of almost all species of farmed fish, and have proven to be as equally nutritionally valuable to fish as commercial feed.

Europe has finally been given the green light to at least partly replace commercial fish feed with sustainable insect sources of protein from July 2017. Yet the insects are currently considered ‘farmed animals’ and therefore have to be reared on expensive commercial feed. Insects of many species are the ultimate natural convertors of organic waste into protein- and lipid-rich larvae. However, animal manure or catered food waste as insect feed, often used in the developing world, pose a risk of introducing dangerous bacteria to the insects, the fish and, eventually, human consumers.

So what could the insects be fed instead? The Aquafly project, led by the National Institute of Nutrition and Seafood Research, Norway, had a brilliant idea…. how about seaweed?! It’s an abundant organic material which would provide a source of Omega-3 for the insects, the fish and, ultimately, human consumers.

Then there was the choice of insects. A tropical, terrestrial species called Black Soldier Fly was an obvious choice as it’s already reared on an industrial scale in Europe for livestock and pet feed, the larvae contain very high protein and fat levels, and the adult fly does not transmit disease to humans.

A University of Stirling PhD, my role in the Aquafly project is to evaluate the risk of environmental bacteria, which may prove dangerous to human consumers, entering this highly novel feed and food chain. Essentially, how safe are your salmon fillets if they’ve been fed fly larvae which have been wholly or partly reared on seaweed?

Several big commercial and research partners got on board with this project. Ocean Harvest in Ireland was responsible for providing powdered seaweed. Protix Biosystems in the Netherlands reared the Black Soldier Fly larvae partly on the seaweed supplement. EWOS Innovation in Norway produced fish feed pellets using the larvae meal. Finally, GIFAS in Norway will undertake the feeding trials using sustainably farmed Atlantic salmon this year.

Since last year, I’ve been lucky enough to visit the first three of these companies, and see the inner workings of innovative animal feed production, as I followed the seaweed powder and larvae products throughout the industrial processing chain. The general public rarely get to experience the cutting edge of research and industry working together! My microbiological screening of the freshly harvested seaweed, and raw ingredients fed to the larvae, through to the fish feed pellets showed that seaweed is an entirely microbiologically safe feed ingredient for insect larvae. It was also clear that feed pellets produced using Black Soldier Fly larvae as a protein source were free of any bacteria dangerous to humans. A great result for Aquafly!

The final stage of the project is now fast approaching… the Atlantic salmon feed trials in northern Norway. Will the salmon fillets be safe for consumers to eat? Check back here soon for the next exciting instalment…

The long-term environmentally and economically sustainable production of Atlantic salmon is essential to both Scotland and Norway’s economies. This PhD research project is Match-funded by the University of Stirling and the National Institute of Nutrition and Seafood Research, Norway.

To find out more about the Aquafly project, follow the link:

https://www.nifes.no/en/prosjekt/insects-salmon-feed/

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