Effects of Different Dietary Starch Levels on Growth and Energy Metabolism of Juvenile Chinese Mitten Crab ( Eriocheir sinensis ) Based on Metabolomic Analysis

Starch is a critical energy source in the nutrition of aquatic animals and significantly influences the physiological and metabolic characteristics of the organism. Therefore, determining an appropriate dietary starch level is of great significance for analyzing the nutritional requirements of Eriocheir sinensis . This study aimed to evaluate the effects of different dietary starch levels on growth and energy metabolism in E. sinensis and to identify an appropriate dietary starch level. A total of 150 healthy E. sinensis with an initial weight of 9.49 ± 0.11 g were selected and divided into five groups with different starch levels: 12%, 17%, 22%, 27%, and 32%. Each group consisted of three biological replicates, with 10 experimental crabs per replicate. After the 60‐day feeding trial, samples were collected for the determination of energy metabolism–related enzyme activities and gene expression levels. Targeted metabolomics was employed to measure the content of energy metabolites in the muscle of experimental crabs under different dietary starch levels. The results indicated that the growth performance of E. sinensis varied significantly with different dietary starch levels ( p < 0.05), exhibiting a trend of initially increasing and then decreasing with higher starch levels, with the best growth observed in the group with a starch level of 22%. Regarding energy metabolism, the enzyme activities of hexokinase (HK), pyruvate kinase (PK), and others showed a trend of initially increasing and then decreasing with rising dietary starch levels, and the differences in related gene expression levels were significant ( p < 0.05). The expression levels of key genes in the adenosine monophosphate (AMP)–activated protein kinase ( AMPK ) and target of rapamycin ( TOR ) pathways also showed significant differences under different starch levels in the feed ( p < 0.05). Among the 26 energy metabolites obtained by energy metabolomics, 16 metabolites, including flavin mononucleotide (FMN), cyclic AMP (cAMP), and nicotinamide adenine dinucleotide (NAD), reached their highest levels when the starch level in the feed was 22%. The experimental results preliminarily showed that the growth of E. sinensis was significantly different under different starch levels in the feed, which was speculated to be related to the active regulation of energy metabolism pathways. When the starch level in the feed was 22%, E. sinensis grew better and accumulated more energy metabolites. These findings provide a scientific reference for starch inclusion in diets for E. sinensis .