Salmon feeds, astaxanthin

Since animals cannot synthesize carotenoids, the pigments must be supplemented in the feeds of farmed species. Salmon and trout farming is now a huge business and feeding studies have shown that astaxanthin is very effective as a flesh pigmenter ... 

Christiansen, R., Lie, O., and Torrissen, O.J., Growth and survival of Atlantic salmon, Salmo salar L, fed different dietary levels of astaxanthin first-feeding fry, Aquacult. Nutr., 1, 189, 1995. 

Noninvasive methods were also used to establish whether the absorption and deposition of astaxanthin are affected by feeding the fish with or without astaxanthin supplementation in all or alternated meals (Wathne et al., 1998). The redness a of the salmon fed with astaxanthin in alternating meals was higher than that for fish fed with a mixture of colored and uncolored meals. A variation in the lightness L was also observed. Wathne et al. (1998) found that the total carotenoid concentration in the flesh could be estimated using the value a. However, the equation cannot be applied for the determination of the carotenoid content in other studies because the value of the coefficients depended on the fish physiological state and on the fish taxon. 

In nature, astaxanthin is usually found either conjugated to proteins (as in the flesh of salmon or in the lobster carapace) or esterified with fatty acids (as in Haematococcus pluvialis microalgae). In contrast, synthetic astaxanthin is produced in the free form. Synthetic, algae-based, and yeast-based (from Xanthophyllomyces dendrorhous) astaxanthins are distinct in their stereoisomeric compositions as well." Synthetic astaxanthin, as well as all three significant natural sources Haematococcus, Xanthophyllomyces, and extracted cmstacean shells), are used widely as feed additives." Human dietary astaxanthin supplements derived from these three natural sources have also been marketed in recent years. " ... 

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