The differential responses of two strains of blunt snout bream (Megalobrama amblycephala) to different dietary carbohydrate levels with insights from transcriptome analysis

This study aimed to investigate the effects of different carbohydrate diets on growth performance, plasma biochemical index and liver transcript alterations in different strains of Megalobrama amblycephala . Fish were fed diets containing 15 %, 30 % and 45 % carbohydrates for 120 days with initial mean weight 42.6 ± 12.1 g per fish. For each net cage, three samples of fish were randomly taken on days 0, 10, 20, 30, 45, 60 and 120 after the start of the experiment. The weight gain rate (WGR) and specific growth rate (SGR) of artificially created strain (AS) in the 30 % group were significantly higher than those in the 15 % and 45 % groups ( p < 0.05). Based on SGR, the appropriate carbohydrate requirements for CP and AS of M. amblycephala were determined to be 26.40 % and 32.50 %. An opposing trend in glucose regulation was observed between common breeding population (CP) and AS during the period from day30 to day45, leading to the performance of RNA-seq analysis. Transcriptome analysis revealed differential regulation of genes involved in carbohydrate metabolism between the strains, suggesting divergent molecular adaptations to carbohydrate utilization. • Based on SGR, optimal dietary carbohydrate for CP and AS were 26.40 % and 32.50 %. • Opposing glucose regulation trends existed between CP and AS from day30 to day45. • Liver RNA-seq revealed divergent strain-specific gene expression patterns.