December 21, 2022

Study shows genetics, feed composition, and stress affect salmon pigment colouration

Research from the Norwegian University of Life Sciences has found that genetics, feed composition, and stress affect the pigment colouration of farmed salmon, as pale or uneven red colour in salmon muscle is increasingly being reported as a quality problem for Norwegian farmed salmon, Fish Information & Services reported.

Fish farmers are reporting the lowest pigment levels ever measured in Norwegian farmed salmon, as colours steadily fade in recent years. More information is required to identify alternative solutions because increasing the pigment addition to feed does not appear to resolve the issue.

Salmon likely consume astaxanthin as an antioxidant to cope with stress. The amount of astaxanthin in the feed has been increased to address the pigmentation issue, but due to the low rate of absorption through the intestine, this has not sufficiently improved muscle coloration.

Experiments conducted by the Norwegian University of Life Sciences found that the most crucial gene influencing pigmentation is likely the beta-carotene oxygenase 1-like gene. Additionally, astaxanthin metabolism and the underlying gene synthesis pathways were discovered through gene expression analysis to be related to cholesterol biosynthesis, vitamin D synthesis, and lipid metabolism.

The findings might suggest that the switch from marine to plant-based diets may have affected astaxanthin metabolism as well, given that diets high in vegetable oils affect genes that regulate lipid metabolism.

After repeated starvation and hypoxia prior to slaughter, the seawater experiment revealed no loss of astaxanthin or fillet colour in salmon. This finding held true for both the red and the white genetic lines. In comparison to non-stressed controls, the fish in the stress-exposed groups also had lower body weight and fitness factors.

Through experiments with fish using various genetic lines selected for different degrees of coloration, the project has discovered significant molecular mechanisms and genes that control pigment coloration in salmon muscle.

The experiment also showed that repeated stress has a detrimental impact on production, but that this is independent of pigmentation. The overlapping gene networks that regulate lipid and astaxanthin metabolism show that various sources of fat in the feed may be crucial for producing satisfactory pigmentation in farmed salmon.

-      Fish Information & Services