Influence of Dietary Soy Lecithin Levels on Growth and Gonadal Development in Male Procambarus clarkii

Abstract: This study evaluates how graded dietary soybean lecithin levels influence growth, lipid metabolism, gonadal development, and antioxidant capacity in male red swamp crayfish (Procambarus clarkii). The results provide a scientific basis for optimizing crayfish feed formulations. In a 60-day trial (July-August), crayfish were divided into five dietary soy lecithin (SL) level groups 0% , 2%, 3%, 4%, and 5% (designated as Groups S1, S2, S3, S4, and S5). The following conclusions were drawn: The hepatosomatic index (HSI) was highest in S3 (P<0.05). Chitinase (CHI) mRNA expression peaked in S2 and S5 (P<0.05), whereas molt-inhibiting hormone (MIH) mRNA peaked in S4 (P<0.05). In the hepatopancreas, Group S4 exhibited the highest contents of saturated fatty acids (SFA), n-3 polyunsaturated fatty acids (n-3 PUFA), long-chain polyunsaturated fatty acids (LC-PUFA), arachidonic acid (ARA), eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA), and docosahexaenoic acid (DHA) (P < 0.05). Catalase (CAT) activity and malondialdehyde (MDA) content peaked in S2, exceeding those in S1, S3, and S5 (P < 0.05). Total antioxidant capacity (T-AOC) and superoxide dismutase (SOD) activities were highest in S3, surpassing those in S1, S4, and S5 (P < 0.05). Low-density lipoprotein receptor (LDLR) mRNA peaked in S3 (P < 0.05). Fatty acid-binding protein (FABP), fatty acid synthase (FAS), and acetyl-coA carboxylase 2 (ACC2) transcripts were highest in S3 and S4 (P<0.05). Omega-6 polyunsaturated fatty acid (n-6 PUFA) content and the DHA/EPA ratio peaked in S3. The n-3/n-6 ratio was greatest in S4. Serum low-density lipoprotein cholesterol (LDL-C) and total cholesterol (TC) peaked in S5 (P<0.05); adipose triglyceride lipase (ATGL) activity was significantly lower in S4 and S5 than in S1 (P<0.05). Gonadal hormones testosterone (T), estradiol (E2), and methyl farnesoate (MF) peaked in S4, whereas progesterone (P4) was lowest (P<0.05). Transcripts of estrogen-related receptors (ERR), heat shock protein 70 (HSP70), 17β-hydroxysteroid dehydrogenase (17β-HSD), steroidogenic acute regulatory protein (StAR), and vitellogenin receptor (VgR) peaked in S4 (P<0.05), as did insulin-like androgenic gland hormone (IAG), heat shock protein 90 (HSP90), and vitellogenin (Vg), all exceeding S1 (P<0.05). Testicular sections revealed maximal sperm deposition in S4 and S5. Blood SOD and MDA peaked in S4, exceeding S2 and S3 (P<0.05). SL dose-dependently modulates nutrition in male P. clarkii. Supplementing 3-4% during the rapid growth phase optimizes growth, antioxidant capacity, and metabolism. During the fattening phase, a brief 4-5% inclusion improves fattening efficiency.