This study was conducted to determine the effects of feeding frequency on the growth, serum biochemical parameters, antioxidant status and hepatic growth hormone (GH), insulin-like growth factor I (IGF-I), lipoprotein lipase (LPL) and hepatic lipase (HL) gene expression levels of juvenile largemouth bass (Micropterus salmoides) reared in an in-pond raceway recirculating culture system (IPRS). Fish (initial body weight 5.0 ± 0.4 g) were hand-fed with a commercial diet under one of three different feeding frequency treatments (2, 3 or 4 meals/day) for 120 days. The results indicated that no significant differences were observed in the final body weight, weight gain and specific growth rate of fish fed different feeding frequencies on 30 days and 60 days (P > 0.05). Fish fed 2 times/day had higher growth than that fed 4 times/day on 90 days but had higher growth than those fed 3 and 4 times/day on 120 days. No significant differences were found in serum alanine aminotransferase (ALT), aspartate transaminase (AST), alkaline phosphatase (ALP) activities, total protein (TP), lysozyme and triglyceride (TG) content, hepatic total antioxidant capacity (T-AOC), glutathione peroxidase (GSH-PX) activities and malondialdehyde (MDA) content among fish fed different feeding frequency (P > 0.05). Serum glucose (Glu) content and catalase (CAT) activity decreased, while total cholesterol (TC) content increased with increasing feeding frequency. Fish fed 2 times/day had higher hepatic total superoxide dismutase (T-SOD) than that fed 4 times/day on 60 days, 90 days and 120 days (P < 0.05). Fish fed 2 times/day had higher IGF-1 gene mRNA expression on 30 days, 60 days and 120 days (P < 0.05), while no significant difference on 90 days. No significant difference was found in GH gene mRNA expression on 30 days and 60 days, while fish fed 4 times/day had lower values than that fed 2 times/day on 90 days and 120 days (P < 0.05). Fish fed 2 times/day had significantly higher LPL mRNA expression level than that fed 4 times/day on 60 days and 90 days and had significantly higher HL mRNA expression level on 60 days, 90 days and 120 days (P < 0.05). Based on growth, physiology, hepatic gene expression levels, labour costs and intensity, the optimal feeding frequency of largemouth bass (average body weight 5.0 ± 0.4 g) reared in IPRS is 2 times/day. These data are very necessary for the optimizing of culture conditions and feeding management strategy in IPRS culture operations.

这项研究旨在确定喂养频率对生长，血清生化参数，抗氧化剂状态和肝生长激素（GH），胰岛素样生长因子I（IGF-1），脂蛋白脂肪酶（LPL）和肝脂肪酶（ HL）基因表达水平的少年大嘴鲈（Micropterus salmoides）养在池塘里的水道循环培养系统（IPRS）中。将鱼（初始体重5.0±0.4 g）以商业饮食人工喂养，采用三种不同的饲喂频率处理（每天2、3或4餐）之一，持续120天。结果表明，在30天和60天饲喂不同饲喂频率的鱼的最终体重，体重增加和比生长率没有显着差异（P > 0.05）。每天饲喂2次的鱼比90天饲喂4次/天的鱼有更高的生长率，但比饲喂120天3和4次饲喂/天的鱼更高的生长。血清丙氨酸氨基转移酶（ALT），天冬氨酸转氨酶（AST），碱性磷酸酶（ALP）活性，总蛋白（TP），溶菌酶和甘油三酸酯（TG）含量，肝总抗氧化能力（T-AOC），谷胱甘肽过氧化物酶（GSH-PX）鱼之间的活动和丙二醛（MDA）进料含量不同的进料频率（P > 0.05）。血清葡萄糖（Glu）含量和过氧化氢酶（CAT）活性降低，而总胆固醇（TC）含量随饲喂频率增加而增加。每天饲喂2次的鱼在60天，90天和120天时的肝脏总超氧化物歧化酶（T-SOD）高于每天饲喂4次的鱼（P  <0.05）。每天饲喂2次的鱼在30天，60天和120天时具有较高的IGF-1基因mRNA表达（P  <0.05），而在90天时无显着差异。在30天和60天时GH基因mRNA表达没有显着差异，而每天喂4次的鱼的值低于在90天和120天每天喂2次的鱼（P <0.05）。每天饲喂2次的鱼的LPL mRNA表达水平显着高于60天和90天每天饲喂4次的鱼，而60天，90天和120天HL mRNA表达水平显着更高（P  <0.05）。根据生长，生理，肝基因表达水平，人工成本和强度，在IPRS中饲养的大嘴鲈（平均体重5.0±0.4 g）的最佳饲养频率为每天2次。这些数据对于优化IPRS养殖操作中的养殖条件和饲喂管理策略非常必要。