March 20, 2007

Farmed salmon require 30 percent more lysine

Farmed salmon, which are increasingly fed on plant protein, need 30 percent more lysine than previously thought, according to Norwegian scientists.

The Norwegian National Institute of Nutrition and Seafood Research (NIFES)has developed a new feed, which shows that salmon with insufficient lysine are fattier than those who do.

Fishmeal used to be the main source of proteins in salmon feed.

In today's farms, more than half of what used to be fishmeal is now replaced with plant proteins as costs escalate and marine resources become scarcer.

Fishmeal contains an optimal balance of the essential amino acids, while a plant protein raw material does not, said Marit Espe, a researcher in the Aquaculture Nutrition Group at NIFES.

A fish feed with high levels of plant proteins may not contain enough essential amino acids and that may affect fish health and growth, Espe said.

NIFES's feed is used to study whether fish feed with high levels of plant protein cover the salmon's need for essential amino acids. The test feed can also be used to study farmed salmon's need for other essential amino acids, when the feed composition is changed to include a large proportion of plant proteins.
 
Farmed salmon weighing 600 grammes were fed the test feed, which contained from very low to very high levels of the essential amino acid lysine.
 

For the same weight, salmon which received inadequate levels of the essential amino acid lysine deposited less proteins and were fattier than salmon receiving enough lysine, the results showed.

The test feed showed that Atlantic salmon weighing 600-1,100 gramnes require 30 percent more lysine than what is recommended today, Espe said.