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Unlocking the true potential of formulated aquafeeds

19 May 2020, at 6:10am

New modelling techniques that measure the digestion dynamics of key nutrients can provide a systematic view of fish nutrition that’s applicable to multiple species and, in the process, help to unlock the potential of a range of aquafeed ingredients.

So explained Dr Dominique Bureau, in a presentation delivered at Alltech’s One Virtual Conference, which gave an overview of the nutritional challenges in commercial aquaculture. A key focus of his talk was how feed trials and formulations often show researchers a small snapshot of a fish’s digestive system, but modelling techniques can add depth to nutritional research.

Dr Dominique Bureau is a Professor a the University of Guelph and co-founder of Wittaya Aqua
Dr Dominique Bureau is a Professor a the University of Guelph and co-founder of Wittaya Aqua

© Wittaya Aqua

The University of Guelph Professor also showed how new sampling and statistical techniques can optimise feed efficiency across multiple species. During his presentation, “On the money: optimising performance and profit with dynamic nutritional modelling”, he illustrated how researchers could systematically predict the digestible or bioavailable nutrients in aquafeed to make more cost-effective and efficient formulations.

A recurring challenge

Designing high-quality and sustainable aquafeeds requires significant investments in research and development and a “one size fits all” option for different fish species is rarely available, he explained.

Aquafeeds contain a huge catalogue of ingredients and functional additives that must be tailored to the needs of different fish species. Researchers also need to contend with the different development stages fish experience before they reach slaughter weight – adding additional complexity to the challenge. Production environments also have a huge bearing on the nutritional success of an aquafeed.

Beyond these production variables, Dr Bureau explains that academic literature and feed trials only show a “mental image” of the effects different feed components have on fish. Though these snapshots are useful, it’s difficult to adapt them into nutrition guidelines. It’s even more difficult to quantify the combined effects of different feed ingredients. Nutritionists and feed formulators need a systematic approach to identify the digestibility of nutrients in aquafeed. This is where dynamic nutritional modelling comes in.

How it works

The first step is to identify all iterations of the nutrient in question and calculate their digestibility coefficients. Though this may sound difficult, published studies and databases like the International Aquaculture Feed Formulation Database contain the information – in many cases, it’s free to access.

After identifying the specific nutrients and digestibility coefficients, researchers should conduct the feed trial with a few adjustments. Instead of measuring the nutrient content of the feed formulation and comparing it to wastes produced after digestion, researchers should sample the chemical dynamics of the fish’s gastrointestinal (GI) tract at various stages after feeding.

By sampling the stomach, proximal intestine and distal intestine, they can track nutrient absorption over time. Since various fish species have different GI anatomies, sampling at these three points brings a species-specific nuance to the reporting. Researchers can also determine how GI morphology affects digestibility, giving feed formulators a more accurate picture of the nutrition dynamics.

Once these data points have been identified, they can be entered into a multiple regression statistical model. The model is able to mimic or predict what was happening during digestion. Dr Bureau explains that: “by adding these chemical and biological process to the three compartments, we could start to understand what was happening in the different parts of the gut at different points in time”.

“So with a simple mathematical model, a few biological and chemical principles and simple mathematical equations, we were able to monitor or model the absorption of [key nutrients] – not just overall but in a different compartments of the GI tract,” he adds.

This model has a welfare benefit as well. Researchers don’t have to open up the fish or conduct an in vitro study to gather the data. “We could simply do it with live fish, feeding normally, behaving normally,” Bureau says.

Potential applications

Though Dr Bureau demonstrated the concept by reviewing the digestion dynamics of phosphorous in rainbow trout, he stressed that the model could be readily applied to other nutrients. The absorption of dietary building blocks like proteins, volatile fatty acids, and micro minerals like copper and selenium could all be modelled and predicted with this system. This not only gives nutritionists stronger data to underpin their feed recommendations but could improve fish performance down the line.

Dynamic nutritional modelling can also be used to explore the efficacy of other gut health solutions like pre- and pro-biotics – allowing producers to see past marketing jargon and make evidence-based decisions about using them.

Dr Bureau, who is also the co-founder of innovative aquaculture software start-up Wittaya Aqua, feels that the combination of background research, experimental work and mathematical modelling gives the model its strength. By using such a model, aquaculture nutritionists will have a more accurate picture of nutrient digestion and the factors that impact the digestive process across multiple species.

He explained that this type of approach will be a valuable tool in examining the dynamics and efficacy of different feed additives and nutritional solutions. As a result, improving gut health and nutrient digestibility for all farmed fish species could be a step closer.