How feed controls pigmentation in salmon

Background

In Norwegian salmon farming, poorer pigmentation of salmon fillets has been observed in recent years despite increased addition of astaxanthin to the feed. This indicates that one can not fully improve the coloration of salmon muscle by increasing the content of astaxanthin in the feed. The result is a downgrading of salmon and losses for the industry.

The red flesh color is characteristic for salmonids, and it is perhaps the foremost quality criterion for  farmed salmon. The color results from binding of astaxanthin to muscle proteins. Astaxanthin is added to the feed and absorbed by the salmon. Usually only about 10% of the astaxanthin in the feed is deposited in the salmon fillet. The reasons for this low utilization rate are both low absorption (digestibility) over the intestine (usually 30-50%) and that much of the absorbed astaxanthin is broken down and excreted.

The decline in pigmentation may be related to changes in the commercial production of salmon in Norway in recent years; These include the transition from feed based on marine ingredients to a feed with mainly plant ingredients. Handling associated with  treatments against salmon lice has also increased in the last decade. Astaxantin is an effective antioxidant, so stress can increase the degradation of astaxanthin. There may also be interaction between these factors, so that the feed composition, affects the salmon’s ability to handle stress.

This project will study how feed composition affects physiological mechanisms that control the pigmentation of salmon muscle and contribute to the development of a feed that secure good and predictable pigmentation of farmed salmon.