Comparison of β-carotene and Spirulina (Arthrospira platensis) in mullet (Mugil liza) diets and effects on antioxidant performance and fillet colouration

The addition of pure carotenoids is a common practice in some aquaculture species production since its use in fish feed is known to improve carcass and antioxidant capacity. Spirulina (Arthrospira) cyanobacteria are a rich source of carotenoids that has proven health benefits for fish welfare. In the current experiment, four isonitrogenous (38%) isolipidic (9%) diets were made, including a control diet (free of β-carotene and Spirulina, SP0), β-carotene diet (50 mg kg−1, β0), and two Spirulina (Arthrospira platensis) diets with 2% (SP2) and 4% (SP4) of total feed inclusion. The experimental diets were given to juvenile mullets in a controlled recirculation system. The parameters evaluated were growth, colour, total carotene content of muscle, and antioxidant capacity of the liver and muscle. Significant differences were found (p < 0.05) in the final weight, specific growth rate, and feed conversion ratio between the SP0 treatment and the β0, SP2, and SP4 treatments. The colorimetric analysis showed that the redness and carotene deposition in muscle of mullet is statistically the same between β0 and SP4. Mullets fed with Spirulina (SP2 and SP4 treatments) had a statistical higher antioxidant capacity against radical peroxyls in liver tissue, showing lower lipid peroxidation (TBARS). In conclusion, Spirulina can be a suitable substitute for pure β-carotene addition in fish diets, improving some of the health benefits from this carotene.