Salmon require more lysine than previously thought – Fishupdate.com
Salmon require more lysine than previously thought Published: 19 March, 2007
Lysine
NIFES has developed a new feed, which shows that farmed salmon need 30% more of the essential amino acid, lysine than previously thought: salmon that don’t get enough lysine are fattier than those who do.
Fishmeal used to be the main source of proteins in salmon feed. Today, however, more than 50% of this is often replaced with plant proteins, because of the great strain on traditional marine raw materials.
Fishmeal contains an optimal balance of the essential amino acids, while a plant protein raw material does not. A fish feed with high levels of plant proteins may result in a fish feed that does not contain enough essential amino acids. This may influence fish health and growth, says Marit Espe, researcher in the Aquaculture Nutrition Group at NIFES.
NIFES has developed a feed that can be used to study whether fish feed with high levels of plant protein cover the salmons need for essential amino acids.
A suitable test feed has to contain low levels of fishmeal and high levels of plant proteins to allow for a low lysine containing feed.
The feed must appeal to the fishs appetite, and the fish must grow well on the test feed in order to enable a comparison between this fish and fish given a feed made from marine raw materials.
In a test, Atlantic salmon in seawater with a starting weight of 300 grams, were fed six different feeds. The fish meal was totally or partially replaced with plant proteins (wheat, gluten and corn). The feed with 5% fishmeal, 5% hydrolysed fish protein and 3% squid hydrolysate turned out to be well suited for studying amino acid metabolism in salmon, says Espe.
The test feed had an amino acid profile similar to the control feed, but with the possibility of varying the levels of desired amino acids. Farmed salmon weighing 600 grams were fed the test feed, which in this case contained from very low to very high levels of the essential amino acid lysine.
The results showed that salmon which received inadequate levels of the essential amino acid lysine deposited less proteins and were fattier than salmon receiving enough lysine. The weights of fish fed on two different feds were similar, says Espe.
The test feed showed that Atlantic salmon weighing 600-1,100 grams actually need 30% more lysine than what is recommended today, she says in closing.
The recommendations comply with NRC 1993. The test feed can also be used to study farmed salmons need for other essential amino acids, when the feed composition is changed to include a large proportion of plant proteins.
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