The present study evaluated the enhancement of the growth rate, intestinal health, immune-related genes, and resistance against suboptimal water temperature in common carp (2.01 ± 0.02 g) by dietary paraprobiotics. Fish were fed dietary heat killed Lactobacillus plantarum (LP20) at 0 (control), 50, and 100 mg/kg for 2 months. After the feeding trial fish were exposed to suboptimal water temperature averaged 13.22 ± 0.44 °C for 48 h. The final body weight, weight gain, specific growth rate, and feed conversion ratio of fish fed LP20 at 100 mg/kg were significantly enhanced (P < 0.05). The villi length and width were increased in fish fed LP20 at 50 and 100 mg/kg when compared to the control (P < 0.05). The crypt depth was increased by increasing LP20 in a dose dependent manner with the highest value in the group of fish fed 100 mg/kg (P < 0.05). The number of goblet cells showed higher number in fish fed LP20 at 50 and 100 mg/kg than the control group (P < 0.05). The expression of catalase (CAT) gene did not show any changes in transcription before the thermal stress however after thermal stress fish fed 50 mg/kg had upregulated CAT followed by those fed 100 mg/kg. Glutathione peroxidase (GPx) and superoxide dismutase (SOD) gene expressions showed upregulations in fish fed 50 mg/kg before the thermal stress but after the thermal stress fish fed 100 mg/kg had the highest level of mRNA transcriptions for GPx and SOD genes. In the same manner, the expression of interleukin 1β (IL-1β), tumor necrosis factor α (TNF-α), and interleukin 10 (IL-10) were significantly upregulated in fish fed LP20 at 50 mg/kg before the thermal stress whereas the expression of these genes was upregulated in fish fed 100 mg/kg. In conclusion, using LP20 at 50−100 mg/kg resulted in enhancing the growth rate, intestinal morphometry, immune and antioxidative related genes. Accordingly, common carp showed high resistance against suboptimal water temperature stress.

本研究评估了膳食副益生菌对鲤鱼（2.01±0.02 g）的生长速度，肠道健康，免疫相关基因以及对次适水温的抵抗力的提高。在0（对照），50和100 mg / kg的条件下，给鱼类喂食膳食热杀死的植物乳杆菌（LP20），持续2个月。喂食试验结束后，将鱼暴露于平均温度为13.22±0.44°C的次优温度下48小时。以100 mg / kg饲喂LP20的鱼的最终体重，体重增加，比生长率和饲料转化率显着提高（P <0.05）。与对照组相比，以50和100 mg / kg饲喂LP20的鱼的绒毛长度和宽度增加了（P<0.05）。通过以剂量依赖的方式增加LP20来增加隐窝深度，在饲喂100 mg / kg的鱼群中隐窝深度最高（P <0.05）。以50和100 mg / kg饲喂LP20的鱼的杯状细胞数高于对照组（P <0.05）。过氧化氢酶（CAT）基因的表达在热应激之前没有显示任何转录变化，但是在热应激后，饲喂50 mg / kg的鱼的CAT上调，其次是饲喂100 mg / kg的鱼。谷胱甘肽过氧化物酶（GPx）和超氧化物歧化酶（SOD））基因表达显示在热应激前饲喂50 mg / kg的鱼中表达上调，但在热应激后饲喂100 mg / kg的鱼中GPx和SOD基因的mRNA转录水平最高。同样，白介素1β（IL-1β），肿瘤坏死因子α（TNF-α）和白介素10（IL-10）的表达在热应激之前，以50 mg / kg饲喂LP20的鱼中的）显着上调，而以100 mg / kg饲喂的鱼中这些基因的表达被上调。总之，以50-100 mg / kg使用LP20可提高生长速度，肠形态，免疫和抗氧化相关基因。因此，鲤鱼对次优水温胁迫表现出高抗性。