Effects of dietary protein and lipid levels on the growth performance, digestive enzyme activities, and hepatopancreatic health of red swamp crayfish (Procambarus clarkii)
摘要
This study evaluated the interactive effects of dietary lipid and protein inclusion levels on the growth performance, nutrient utilization efficiency, and hepatopancreatic physiological status in red swamp crayfish. Two lipid levels (5.0% and 7.0%) and four protein levels (30.0%, 33.0%, 36.0%, and 39.0%) were tested in a 4 × 2 factorial arrangement, with 720 crayfish (7.23 ± 0.01 g) distributed across eight treatments for an 8-week period. The present results demonstrated that crayfish given a 39% crude protein diet yielded the best growth performance, with crayfish exhibiting significantly higher FBW and improved FCR compared to the 30% protein group. Moreover, dietary lipid supplementation (7%) significantly enhanced lipase and Na+ K+ ATPase activity, whereas higher protein levels (36.0% and 39.0%) markedly upregulated amylase and trypsin activities. Dietary lipid supplementation increased triglyceride and aspartate aminotransferase levels. Hepatopancreatic histology observation showed tighter hepatic tubule arrangement and higher F cell counts at 7% lipid and 33% protein, with increased lipid droplet accumulation at 7% lipid groups. The mRNA expression levels of lipid metabolism–related genes peaked at 33% protein diets, while dietary lipid supplementation suppressed their expression except for carnitine palmitoyl transferase (P < 0.05). To conclude, while a 39% protein/7% lipid diet maximized growth, a 33% protein/7% lipid diet is recommended as the optimal formulation, achieving an excellent balance of growth performance, feed efficiency, hepatopancreatic health, and cost-effectiveness for Procambarus clarkii aquaculture.