Different colourant and colourant inclusions in diets for Atlantic salmon and its effect on flesh colour was tested. Experimental diets of similar nutritional composition, but different colourant sources and inclusions were produced in commercial fish feed mill (Laxa ltd.). Panaferd-AX colourant was compared to standard colouring regime using Lucantin® Pink (30/60/50mg/kg) as a control. Atlantic salmon were fed these diets in a growth trial in experimental tanks in saline water for 438 days.
The original plan was to test the colourant Aquasta® in addition but since its production was halted, it was only used in the first phase of the experiment. The continuing experiment compared Panaferd in different inclusion and Lucantin® Pink. Initially The recovery of the colorants in the experimental feed production was tested. Using Panaferd, the recovery of astaxanthin was only 76,9% after feed processing and extrution compared to 100+% recovery using Lucantin. Therefore the experimental diets were added plus 30% colourantsto ensure astaxanthin level according to feed analyses.
To adjust planned colourant consumption the feeding was mixed with unpigmented basal diet. The growth, feed intake and feed conversion were similar between groups, and no mortalities were related to treatments during the experimental period.
The flesh colour was measured by DSM Salmofan®, Konica Minolta CR-400 Chroma Meter and by chemical analyses of astaxanthin and sum of carotenoids. Only small differences were found in visual filet pigmentation, measured by Salmofan and Konica Minolta Chromo Meter, between the different colouring regimes. The filet colour was considered acceptable in all treatment groups. The correlation between chemically analysed content of carotenoids, including astaxanthin, and visual colour score of the filets was poor.
In conclusion: all tested regimes and carotenoid content in the diets for Atlantic salmon resulted in acceptable fillet colour.