Fattening culture improves the gonadal development and nutritional quality of male Chinese mitten crab Eriocheir sinensis

Abstract

The Chinese mitten crab, Eriocheir sinensis, is an important aquaculture species in China, and >80% of aquaculture production comes from outdoor earth-ponds. Fattening immature E. sinensis with a high-quality diet has been proven to effectively improve male gonadal development and nutritional value. This study aimed to investigate the effects of different fattening periods on male gonadal development and nutritional quality of pond-reared male E. sinensis post pubertal molting. The gonadosomatic index (GSI) increased significantly during the 60-day fattening period, while significant increases in meat yield and total edible yield were only found between Day 0 and Day 20. The gonadal system, consisting of testis, deferens and accessory gland, had the highest increase during the fattening period. The fattening period did not significantly affect the proximate composition of hepatopancreas; however, the protein contents of male gonad and muscle increased significantly. The moisture and carbohydrate contents of the gonad, as well as muscular moisture, decreased significantly during the 60-day fattening period. A significant decrease in gonadal lipid contents was found between Day 40 and Day 60, while the trend of “low-high-low” was found in muscular carbohydrate levels during the whole fattening period. Significant increases were found in the percentage of triglyceride (TG) and free fatty acids (FFA) in male gonad, while decreases were found in the percentages of cholesterol and phospholipid in male gonads, FFA in hepatopancreas and TG in meat during the 60-day-fattening period. With respect to fatty acid composition, a trend of “high-low-high” was found for the percentages of mono-unsaturated fatty acids (MUFA), poly-unsaturated fatty acids (PUFA) and long chain poly-unsaturated fatty acids (LC-PUFA) in male gonad and hepatopancreas. The percentages of saturated fatty acid (SFA) and MUFA in muscle decreased significantly, while the significant increases were found in muscular PUFA and LC-PUFA during the fattening period. Total amino acid (TAA) levels of male gonads increased dramatically during the fattening period, and essential amino acid scores of male gonad and muscle were >100 for all essential amino acids (EAA) after the 60-day fattening period. In conclusion, these results suggest that an appropriate fattening period is approximately 40 days for pond-reared male E. sinensis post pubertal molting.