投喂频率对池塘工程化循环水养殖大口黑鲈生长、生理及肝脏GH、IGF-I基因表达丰度的影响

为研究池塘工程化循环水养殖模式下投喂频率对大口黑鲈(Micropterussalmoides)生长、生理及肝脏生长激素基因(GH)、类胰岛素生长因子-I基因(IGF-I)相对表达丰度的影响,选用初始体重为(5.0±0.4) g的大口黑鲈为研究对象,设置3个投喂频率组(2次/d、3次/d、4次/d),每组3个重复,开展为期120 d的养殖试验。结果表明,第30天和第60天时,大口黑鲈末体重、增重率和特定生长率均未受到投喂频率的显著影响(P0.05),而在第90天时, 2次/d组试验鱼的生长显著高于4次/d组(P0.05),与3次/d组相比无显著性差异(P0.05);第120天时, 2次/d组试验鱼的生长显著高于3次/d组和4次/d组(P0.05);投喂频率对血清谷氨酸氨基转移酶(ALT)、天门冬氨酸氨基转移酶(AST)、碱性磷酸酶(ALP)活性、溶菌酶、皮质醇和甘油三酯(TG)含量、肝脏总抗氧化能力(T-AOC)、谷胱甘肽过氧化物酶(GSH-Px)活性及丙二醛(MDA)含量均无显著性影响(P0.05)。随着投喂频率的增加,肝脏过氧化氢酶(CAT)活性及血清总蛋白(TP)、血糖(Glu)含量呈降低的趋势且血清总胆固醇(TC)呈上升的趋势;第30天时投喂频率对肝脏总超氧化物歧化酶(T-SOD)活性无显著性影响,而第60天、第90天和第120天时,4次/d组T-SOD活性显著低于2次/d组(P0.05)。第30天、第60天和第120天时, 2次/d组肝脏IGF-I基因的相对表达量最高(P0.05),第90天时各组间肝脏IGF-I相对表达量无明显差异(P0.05);第30天和第60天时,肝脏GH基因相对表达量未受到投喂频率的影响(P0.05),而第90天和第120天时4次/d组肝脏GH基因相对表达量显著低于2次/d组(P0.05)。因此,基于大口黑鲈的生长性能、生理效应及肝脏GH、IGF-I基因表达丰度的综合考虑,池塘工程化循环水养殖模式下初始体重为(5.0±0.4)g的大口黑鲈适宜投喂频率为2次/d。

Effects of feeding frequency on the growth, physiology and expression abundance of IGF-I and GH mRNA in largemouth bass (Micropterus salmoides) reared in in-pond raceway culture systems

A 120-day experiment was conducted to investigate the effects of different feeding frequencies on the growth, physiology, and hepatic growth hormone (GH) and insulin-like growth factor-I (IGF-I) gene expression levels of Micropterus salmoides (body weight:5.0 g±0.4 g) reared in in-pond raceway culture systems (IPRS). Fish were randomly assigned to one of three feeding frequencies (2, 3 and 4 times/d) following the same ration size. No significant differences were observed in final body weight, weight gain or specific growth rate of fish fed at different feeding frequencies on days 30 and 60 (P>0.05). Fish fed 2 times/d showed higher growth than those fed 4 times/d on day 90, and had higher growth than those fed 3 times/d and 4 times/d on day 120. No significant differences were found in serum alanine aminotransferase (ALT), aspartate transaminase (AST), or alkaline phosphatase (ALP) activities, lysozyme, cortisol and triglyceride (TG) content, hepatic total antioxidant capacity (T-AOC), glutathione peroxidase (GSH-Px) activities, nor in malondialdehyde (MDA) content among fish fed at different feeding frequencies (P>0.05). Serum total protein (TP) and glucose (Glu) content, and catalase (CAT) activity, decreased, while total cholesterol (TC) content increased with increasing feeding frequency. Fish fed 2 times/d had higher hepatic total superoxide dismutase (T-SOD) than those fed 4 times/d on days 60, 90 and 120 (P<0.05). Fish fed 2 times/d exhibited higher IGF-I gene mRNA expression on days 30, 60 and 120 (P<0.05), while no significant difference was found on day 90. No significant difference was found in GH gene mRNA expression on days 30 and 60, while fish fed 4 times/d exhibited lower GH gene mRNA expression than those fed 2 times/d on days 90 and 120 (P<0.05). Based on the growth, physiology, and hepatic GH and IGF-I gene expression levels, the optimal feeding frequency for Micropterus salmoides (average body weight:5.0 g±0.4 g) reared in IPRS is 2 times/d. These data are crucial for the optimization of culture conditions and feeding management strategies in IPRS culture operations.