Comparison of effect of dietary supplementation with Haematococcus pluvialis powder and synthetic astaxanthin on carotenoid composition, concentration, esterification degree and astaxanthin isomers in ovaries, hepatopancreas, carapace, epithelium of adult female Chinese mitten crab (Eriocheir sinensis)

Astaxanthin is widely used in aquaculture, being added to feeds to give desirable coloration to the farmed animals. Little is known about the different effects of natural and synthetic astaxanthin on Chinese mitten crab (Eriocheir sinensis). This study was conducted to compare the effects of dietary supplementation with Haematococcus pluvialis powder and synthetic astaxanthin on carotenoid composition, concentration, degree of esterification and astaxanthin isomers of E. sinensis. Six experimental diets were formulated including a basal diet, three diets containing H. pluvialis powder (0.2%, 0.4%, 0.6%) and two diets containing synthetic astaxanthin (0.13%, 0.16%), with each diet being fed to female crabs (average body weight of 85 +/- 5 g) in triplicate tanks with 12 crabs in each. After feeding for 30 and 60 days, the ovaries, hepatopancreas, carapace and epithelium of 3 crabs from each tank were taken for carotenoid analysis. Dietary supplementation with H. pluvialis powder and synthetic astaxanthin increased the astaxanthin concentration of E. sinensis in a dose-dependent manner. After 60 days, the astaxanthin concentration in body parts of crabs from high to low were ovaries (45.19-343.37 mg/kg), epithelium (14.98-37.74 mg/kg), carapace (12.86-21.71 mg/kg) and hepatopancreas (0.49-8.75 mg/kg). Astaxanthin in the epithelium was found in esterified form but in other body parts the astaxanthin was not esterified. All-trans astaxanthin was predominant in the ovaries, epithelium and carapace, and the proportion varied from 59.74% to 96.94%. (3S,3'S)-astaxanthin was mostly deposited in the ovaries of crabs fed with diets containing H. pluvialis powder and the proportion (85.18%-96.27%) increased significantly with increasing astaxanthin concentration of diets. Differences of astaxanthin isomers between diets and body parts indicated that isomers were deposited selectively and were likely to be accompanied by isomerization. To achieve the same effect on body astaxanthin concentration, synthetic astaxanthin required a higher level of addition than H. pluvialis powder. These results suggest that H. pluvialis powder is more effective in astaxanthin accumulation of E. sinensis, and also improves carotenoid and astaxanthin isomer composition of E. sinensis in comparison with synthetic astaxanthin.