October 4, 2010

Norwegian scientists solve farmed salmon cataract problem

Eye specialists at the University of East Anglia (UEA) have determined how the nutrient histidine prevents cataracts in salmon.

The nutrient stops cataracts from forming when added to the diet of farmed salmon, according to the study.

The nutrient is present in high quantities in blood meal, which was eliminated from the diet of farmed salmon due to concerns regarding mad cow disease (BSE) in the 1990s, and this led to drastically increasing numbers of fish getting cataracts. Economic losses and fish welfare problems ensued.

During the life cycle of salmon the young salmon parr spend the early part of their life in fresh water before they enter the sea as salmon smolts where they grow to maturity before returning to fresh water to spawn, said Dr Jeremy Rhodes from the Norwich Eye Research group at UEA.

Rhodes explained that histidine has a protective role in the lenses of salmon enabling them to withstand the considerable environmental stresses that their life cycle demands. When histidine is deficient in the diet, these environmental stresses lead to the development of cataract.

Norway is the chief producer of farmed salmon, leading a US$11 billion worldwide industry. It produces a 33% share.

In 2004, a research team was established to investigate the cause of the cataract outbreaks. A multi-centre collaboration launched between the research labs of the UEA's Norwich Eye Research Group and the National Institute of Nutrition and Seafood Research (NIFES) and industrial partners Biomar Ltd and Marine Harvest.

The Norwich Eye Research Group has played a critical role. It has also hosted scientists from the NIFES labs in Norway and sent scientists there to help gather samples and create new techniques.

The dietary histidine has been increased in the diet of farmed salmon as a direct result of this collaborative research, thus having an impact on the international salmon farming sector.

A synthetic histidine compound was recently approved by the European Food Safety Authority (EFSA) for use within the European Union (EU) due to the findings of the research.