Effects of dietary lipid levels on growth performance, muscle composition, reproductive performance and hemolymph biochemical indices of Procambarus clarkii broodstock

The objective of this study was to assess the optimal dietary lipid requirement of red swamp crayfish broodstock(Procambarus clarkia), In present study, 324 crayfish with average initial body weight of (15.46±0.20) g were randomly divided into 6 groups with 3 replicates of 18 crayfish in each replicate. Crayfish in each group were hand-fed a semi-purified diets containing different lipid levels 1.98% (control group), 4.12%, 4.98%, 7.89%, 10.48% and 11.89% for 8 weeks. At the end of feeding trial, growth performance, muscle composition, reproductive performance, activities of digestive enzyme in hepatopancreas, and hemolymph biochemical indexes were measured. The results showed as follow, 1) as dietary lipid level increasing, the weight gain rate(WGR) and specific growth rate(SGR) of crayfish broodstock increased at first and then decreased. The feed conversion ratio(FCR) and hepatosomatic index(HSI) showed a increase trend, and were highest in 11.89% group. 2)The dietary lipid levels did not significantly affect the muscle moisture and ash contents. The lipid content of the muscle gradually increased as dietary lipid level increasing, and then tended to decrease, and was highest in 5.84% group. 3)With the increase of lipid levels, gonad index, egg-carrying rate and egg carrying capacity of crayfish broodstock were increased at first and then decreased; all of them in 7.89% group were highest. 4)The total protein (TP) content of haemolymph trended to decrease as dietary lipid level increasing. Alanine aminotransferase(ALT) activity and aspartate aminotransferase(AST) activity in haemolymph significantly increased as dietary lipid level increasing, both of them in 11.89% group was highest. The dietary lipid level did not significantly affect the glucose content of haemolymph. 5)The dietary lipid level significantly affected the activities of hepatopancreas protease and lipase, but not amylase activities. Broken-line regression analysis using WGR as response criteria shows that the optimal requirement of dietary lipid for red swamp crayfish broodstock is 7.60%. The comprehensive analysis of growth performance, muscle composition, reproductive performance, activities of digestive enzyme in liver, and hemolymph biochemical indexes showed that appropriate lipid level for red swamp crayfish broodstock was 7.60%~7.89% under this trial condition.