Astaxanthin from Phaffia rhodozyma screened by metagenome sequencing improves the growth performance, intestinal health, and immunity of juvenile Opsariichthys bidens

Intestinal flora, known as the "second genome," play an important role in growth, development, barrier protection, and immunological tolerance in aquatic organisms. Intestinal flora of cultured fish can be influenced by various factors such as culture environment, growth stage, growth rate, and gender. In this study, we used a metagenome sequence to analyze the intestinal flora of male and female Chinese hook snout carp ( Opsariichthys bidens ) across different growth stages. This study aims to identify the genera that serve as sources of dietary nutrient supplementation to improve fish health status and growth performance. The results showed no significant differences in the overall intestinal flora of male and female O. bidens . However, variations in the growth stage may cause changes in the dominant phyla and functional dissimilarities between the two genders. Among the identified genera, Phaffia rhodozyma was screened as a genus considered to have the potential for nutrient supplementation. In order to validate its efficacy, varying concentrations of P. rhodozyma were supplemented into the diet to assess the culture performance of O. bidens . Our results demonstrated that the 0.5 % dietary supplementation of P. rhodozyma significantly improved growth performance indicators (WGR, SCR, and FCR) of O. bidens as compared to the control group ( p < 0.05). Moreover, it’s also enhanced the reproductive performance in females as well as increased the antioxidant capacity and immune resistance. Based on growth performance, 0.5 % was determined to be the optimal supplementation level of P. rhodozyma . • Comparative gut microbiota in male/female Opsariichthys bidens at growth stages using metagenomic sequencing. • Phaffia rhodozyma as a potential dietary supplement for aquaculture. • Dietary Phaffia rhodozyma enhanced culture performance of juvenile Opsariichthys bidens . • The optimal concentration of Phaffia rhodozyma supplementation was 0.5 %.