Department of Animal Production, Fish Production, Faculty of Agriculture, Al-Azhar University, Cairo, 11651, Egypt.
Department of Nutrition and Clinical Nutrition, Faculty of Veterinary Medicine, Kafrelsheikh University, 33516, Kafrelsheikh, Egypt.
Fish Shellfish Immunol. 2020 Dec;107(Pt A):277-288. doi: 10.1016/j.fsi.2020.10.015. Epub 2020 Oct 13.
The current work was planned to assess the effects of dietary microalga, Nannochloropsis oculata (NP) on the growth indices, serum biochemistry, non-specific immunity, and resistance of Nile tilapia (Oreochromis niloticus) juveniles against challenge with pathogenic Aeromonas veronii. Fish (10.21 ± 0.28 g) were randomly divided into four treatments in triplicates and were fed on diets supplemented with different levels of NP (0, 5, 10, and 15%) for eight weeks. The results showed that the dietary 5% NP significantly improved the growth parameters (final body weight, weight gain, specific growth rate, and total feed intake) (P < 0.05). Meanwhile, the feed conversion ratio was significantly decreased in NP-supplemented groups with respect to the control group. The serum protein profile (total protein, albumin, globulin, and albumin/globulin ratio) was significantly decreased by 15% NP supplemented group. Meanwhile, liver enzymes (alanine transaminase, and aspartate transaminase) activities were not significantly affected by NP dietary supplementation (P < 0.05). Serum lysozyme activity, nitric oxide (NO), and nitroblue tetrazolium (NBT) levels were significantly enhanced only in 5% NP supplemented group (P < 0.05). Interestingly, the hepatopancreatic and intestinal tissues had apparently normal histomorphology of Nile tilapia fed at 5% NP-supplemented diets. Significant upregulation of cytokines [interleukin 1beta (IL-1β), interleukin 8 (IL-8), interferon-gamma (IFN-γ), transforming growth factor-beta (TGF- β), and tumor necrosis factor-alpha (TNF-α)], with significant downregulation of the antioxidant gene [superoxide dismutase (SOD)] in 10% and 15% NP supplemented groups. Attractively, the relative level of protection (RLP) against challenge with pathogenic A. veronii was significantly elevated in 10% and 15% NP supplemented groups. Conclusively, the obtained results reflect the beneficial roles of dietary NP to improve growth and boost the immune responses of Nile tilapia.
本研究旨在评估饲料微藻盐藻（Nannochloropsis oculata，NP）对尼罗罗非鱼（Oreochromis niloticus）幼鱼生长指标、血清生化指标、非特异性免疫和抗致病性维氏气单胞菌（Aeromonas veronii）能力的影响。将 10.21±0.28g 的鱼随机分成 4 组，每组 3 个重复，分别投喂添加不同水平 NP（0、5、10 和 15%）的饲料 8 周。结果表明，日粮 5% NP 显著提高了生长参数（终体重、增重率、特定生长率和总饲料摄入量）（P<0.05）。同时，NP 组的饲料转化率与对照组相比显著降低。血清蛋白图谱（总蛋白、白蛋白、球蛋白和白蛋白/球蛋白比值）在 15% NP 补充组显著降低。同时，肝酶（丙氨酸转氨酶和天冬氨酸转氨酶）活性不受 NP 日粮添加的影响（P<0.05）。血清溶菌酶活性、一氧化氮（NO）和硝基四唑蓝（NBT）水平仅在 5% NP 补充组显著提高（P<0.05）。有趣的是，5% NP 补充组尼罗罗非鱼肝胰脏和肠道组织的组织形态学明显正常。细胞因子[白细胞介素 1β（IL-1β）、白细胞介素 8（IL-8）、干扰素-γ（IFN-γ）、转化生长因子-β（TGF-β）和肿瘤坏死因子-α（TNF-α）]显著上调，10%和 15% NP 补充组抗氧化基因[超氧化物歧化酶（SOD）]显著下调。有吸引力的是，10%和 15% NP 补充组对致病性 A. veronii 攻毒的相对保护率（RLP）显著提高。总之，研究结果反映了饲料 NP 对提高尼罗罗非鱼生长和增强其免疫反应的有益作用。
