July 29, 2015


Enzymes use in fish feed reduces environmental impact, university body says



Enzymes had demonstrated capabilities in improving the efficiency of nitrogen and phosphorus retention when used in fish feed, a study by Argentina's Agronomy School of University of Buenos Aires (FAUBA) revealed.


As a result, discharges of such nutrients into aquatic environments are reduced. These activities tend to increase due to fish diets with a high amount of vegetable protein and ingredients which also introduce anti-nutritional elements. Hence, protein and mineral bioavailability in fish are significantly compromised.


Therefore, researchers from FAUBA attempted to create nutritional strategies that will base the aquaculture growth of carnivorous fish on the use of protein resources from agriculture by obtaining functional diets which are also safe for the environment.


In addition, diets will be developed with a restricted amount of land-derived vegetable protein alternatives in order to cut down on anti-nutritional factors including phytate and phytic acid, Dr. Gabriel Morales, the professor of aquaculture in FAUBA, said.


"Our strategy from the nutritional point of view is to find a way to release the native phosphorus that is naturally present in the seeds, using enzyme additives and inducing changes in the fish gastrointestinal environment, which makes it possible to increase the absorption and retention of nutrients," he added.


The researchers employed a digestive modeling system in vitro for a more intimate observation of enzyme-substrate interactions.


"This evaluation system is complemented with in vivo trials developed on a pilot scale in fish tanks installed in college," Dr. Morales said. "Subsequently, we test optimised diets under production conditions in trout fattening cages installed at a reservoir in Alicurá, a province of Neuquen (Argentina)."


With enzymatic additives like phytase, Dr. Morales explained that the utilisation of native phosphorus reserves in seeds will be improved as well, leading to a boost in the bioavailability of nutrients. The enzymes will also increase protein retention in fish by stimulating the breakdown of phytate-protein complexes which are found in plant ingredients.


"The phytase has an interesting industrial implementation because of its proven advantages: less use of mineral phosphorus supplements in diets, higher growth, better conversion efficiency, increased phosphorus and nitrogen retention as well as a lower discharge of these nutrients into the environment," Dr. Morales said.


"It is used in chickens and pigs, and we are now evaluating its use in fish."

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