Improved Flesh Pigmentation of Rainbow Trout (<i>Oncorhynchus mykiss</i>) by Feeding <i>Z</i>-Isomer-Rich Astaxanthin Derived from Natural Origin

Abstract

pigmentation efficiency in aquaculture and pose an industrial challenge 6−8) . In recent years, geometric isomerization has attracted attention for enhancing the bioavailability of carotenoids, including astaxanthin (Fig. 1) 9,10) . For example, in vivo studies using rats and guinea pigs showed that oral supplementation with diets rich in astaxanthin Z-isomers resulted in a ＞25-fold increase in astaxanthin concentration in plasma compared to those fed diets rich in the all-E-isomer 11,12) . Furthermore, astaxanthin Z-isomers showed higher egg yolk pigmentation efficiency in laying hens than the all-E-isomer 13) . In contrast, several studies showed that the opposite result was found in rainbow trout (Oncorhynchus mykiss) , that is, (all-E) -astaxanthin exhibits greater flesh pigmentation efficiency in rainbow trout than the Zisomers, which might be due to higher bioavailability of the all-E-isomer in this species 14−16) . For example, Bjerkeng et al. (1997) prepared a diet rich in astaxanthin Z-isomers