Cataracts are a problem that can occur in the eyes of salmon. A cataract is characterised by a cloudiness of the lens and is caused by a special fibre inside the lens swelling and losing its transparency. The cloudiness can occur as a result of inflammation inside the lens. The development of cataracts is also connected with malnutrition, and especially with insufficient amounts of the amino acid histidine in feed. fôret.
Cataracts are first and foremost a welfare problem for fish as they develop poor sight and can go blind. Amongst other things, this means it is more difficult for salmon to take in feed.
Today, we have a large body of knowledge regarding the nutritional need of salmon, and we can prevent cataracts by adding histidine to their feed. In recent years, however, we have faced a new challenge with the increased use of sterile triploid salmon.
This type of salmon has a higher growth rate and it appears that they have adapted their nutritional requirements for maintenance and growth.
Triploid salmon must have specially adapted feed with, amongst other things, increased levels of histidine and phosphorus to prevent the development of cataracts and bone deformities.
Photo: Ellen Bjerkås