Effects of astaxanthin microencapsulated from Haematococcus pluvialis on the growth, muscle quality, antioxidant system, and related gene expression of Cyprinus carpio

This study aims to verify the effects of astaxanthin microcapsules on the growth, physiology, and nutritional value of Cyprinus carpio ( C. carpio ), and evaluate the feasibility and safety of microcapsule technology in aquaculture. In this experiment, natural and synthetic astaxanthin were encapsulated in microcapsules, with empty microcapsules used as a control, and C. carpio was fed these diets for 8 weeks. Growth, muscle quality, and the antioxidant system were then assessed. The results showed that (1) the weight gain rate (WGR), specific growth rate (SGR), and condition factor (K) in group A (natural astaxanthin) and group B (synthetic astaxanthin) were significantly higher than those in the control group, with no significant differences in viscerosomatic index (VSI) or hepatosomatic index (HSI) across the groups. (2) Astaxanthin supplementation enhanced the antioxidant activity in the hepatopancreas of C. carpio . Total superoxide dismutase (T-SOD) activity significantly increased, malondialdehyde (MDA) levels decreased, while no significant changes were observed in total antioxidant capacity (T-AOC) or catalase (CAT) activity. The sod1 and gpx1a genes were significantly upregulated in group A. (3) Astaxanthin also improved muscle nutritional quality by significantly increasing crude protein content, reducing crude ash content, and enhancing water-holding capacity. Amino acid and fatty acid composition also showed improvement. Overall, this study suggests that natural astaxanthin may be superior to synthetic astaxanthin, and provides preliminary evidence that self-made astaxanthin microcapsules are safe for future aquaculture, offering a scientific basis for sustainable and eco-friendly aquaculture practices.