Monday, November 7, 2016

08/11/2016: Aqua feed, shrimp feed reducing marine feedstuff in aquaculture

by Gaëlle Husser, Product Manager AQUAVI® Met-Met, Evonik Nutrition & Care

The proportion of fishmeal in salmon feed has been drastically reduced over recent years—with a positive impact on wild fish stocks and the environment.

Evonik has made a significant contribution to this development with its DL-Methionine for AquacultureTM product, an amino acid-balancing aqua feed supplement. Now this same concept of reducing fishmeal and protein in feed can also be applied to shrimp feed thanks to Met-Met, the dipeptide of DL-methionine.

Shrimp are different
Amino acids dissolve in water. This fact may not sound particularly exciting, yet it has far-reaching consequences. In the past, this precise property was a major feed roadblock.

In shrimp aquaculture around the world, it made it difficult to develop innovative feeding concepts—plant-based protein sources supplemented with free amino acids such as DL-methionine or comparable products, why? Because shrimp eat relatively slowly.

As bottom-feeders, they take about half an hour to nibble their way through a two-millimeter-wide feed pellet.

For water-soluble feed components such as DL-methionine, that is a very long time. It means that a portion of the amino acids gets washed out of the pellet along with water-soluble minerals and vitamins; and the shrimp lose out.

Timing is everything
The crustacean’s digestive system is another obstacle to be overcome when it comes to the optimal conversion of supplemented DL-methionine in protein synthesis.

The shrimp reabsorb the amino acids quite quickly, while at the same time other amino acids from feed components such as soy meal are not yet available to them. This is because shrimp, unlike fish, do not possess a stomach containing hydrochloric acid.

In fish, hydrochloric acid facilitates digestion by denaturalizing proteins and breaking them down into short-chain protein building blocks and amino acids. Shrimp, in contrast, produce enzymes in their hepatopancreas, which break up the proteins into short-chain peptides and amino acids—a process which takes time.

As a result, amino acid supplements in feed, such as DL-methionine and amino acids from protein sources contained in the feed, are made available for digestion by the shrimp at different points in time. This means the animals cannot efficiently convert their feed, excreting it back out as nitrogen-containing waste products.

This is the fate of all amino acids in all organisms if the amino acid spectrum in the feed is not precisely tailored to the organism’s specific requirements—whether too many amino acids are added or too few are contained in the natural feed components.

If one single amino acid is missing, the animal is unable to make use of the existing amino acids for protein synthesis, bringing growth to a standstill.

Particularly in aquaculture, this sets in motion a downward spiraling process: The additional nitrogen burden leads to eutrophication in bodies of water, promotes algal growth and offers the perfect breeding ground for germs.

These can make animals sick, thereby decreasing their ability to convert the feed. When feed conversion declines, even more nitrogen compounds are emitted into the water.

A burden on marine resources
To achieve the desired growth, fish farmers in more conventional shrimp aquaculture respond to these issues by feeding their animals a protein-rich diet. In this type of feeding concept, one kilogram of shrimp requires around 1.6 kilograms of feed.

In such conventional diets for fish and crustaceans, the protein and fat components in the feed are made up of fishmeal and fish oil. Today, some three quarters of all the world’s fishmeal production is used for aquaculture.

This creates a huge burden on marine resources, even though the original goal of aquaculture was to relieve them. For this reason, modern feeding concepts aim to cover part of the protein requirement with plant-based ingredients such as rapeseed or soymeal.

But these components have their limits: The amino acid profile of plants does not meet the needs of animals—it is typically lacking in lysine, methionine or threonine. This amino acid is the first-limiting one for the growth of fish and crustaceans is species-dependent.

Read the full article HERE.

The Aquaculturists
This blog is maintained by The Aquaculturists staff and is supported by the
magazine International Aquafeed which is published by
Perendale Publishers Ltd

For additional daily news from aquaculture around the world: aquaculture-news

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