DIFFERENT ASTAXANTHIN SOURCES ON GROWTH PERFORMANCE, FLESH COLOR, ANTIOXIDANT ABILITY, AND ACUTE NITRITE STRESS OF RAINBOW TROUT (<italic>ONCORHYNCHUS MYKISS</italic>)

The present study investigated the effects of dietary supplementation with astaxanthin from different sources on growth performance, flesh pigmentation, antioxidant capacity, and acute nitrite stress response in rainbow trout (Oncorhynchus mykiss). Four diets were designed as the control diet and three astaxanthin inclusion diets, including 3.0 g/kg Paracoccus carotinifaciens (PC), 2.4 g/kg Haematococcus pluvialis (HP), and 0.6 g/kg Carophyll Pink (CP), each providing 60 mg/kg astaxanthin. A total of 480 rainbow trout with an initial body weight of (6.17±0.08) g were randomly assigned to four groups with four replicates each, followed by a 30-day feeding trial. Results showed that there were no significant differences in growth performance between astaxanthin-supplemented groups and the control group (P>0.05). Muscle redness and yellowness values, as well as astaxanthin content, were significantly higher in all astaxanthin-supplemented groups than that in the control group (PP0.05). Following nitrite challenge, plasma cortisol, glucose, and lactate levels were significantly lower in astaxanthin-fed groups compared to the control (Pnrf2 and sod gene expression and downregulated bcl2 and caspase9 expression. In conclusion, dietary astaxanthin from three different sources improved the flesh color, pigmentation, antioxidant capacity, and anti-stress capacities in rainbow trout. However, PC and CP showed stronger effects in enhancing antioxidant capacity compared to HP, while HP exhibited a greater ability to alleviate cell apoptosis in rainbow trout.