Phytobiotics are promising diet alternatives, yet their effectiveness in high-risk aquaculture conditions remains underexplored. Therefore, a 90-day feeding trial was conducted based on dietary supplementation of Nile tilapia, Oreochromis niloticus, with herbal extracts, namely, lemon balm [Melissa officinalis (MOE)], marjoram [Origanum majorana (OME)], and chamomile [Matricaria chamomilla (MCE)] with 0% water change. The treated groups were compared to groups untreated with herbs or control groups [positive control (PC; 0% water change) and negative control (NC; 20% water exchange per day]. Fish were cultured at stocking density (20 fish m-3: 1.8kg of biomass/m3). We conducted a physicochemical analysis of the water and the clinical responses, growth, and immune responses of the fish were evaluated. Furthermore, the herbal-supplemented fish were then challenged with a pathogenic Edwardseilla tarda strain and mortality was monitored. In the 1st and 2nd months, the water parameters were within the permissible limits. After that, a fatally low dissolved oxygen concentration and the highest levels of ammonia, nitrite, nitrate, and pH were recorded during the 3rd month. Blood and immune assays were conducted in the treated groups and control groups. The herbal-treated groups appeared healthy, but during the 3rd month, lethargy and decreased appetite were evident. Generally, the herbal-treated fish showed improved growth performance parameters, survival rates, and resistance against pathogenic bacteria E. tarda, particularly in the OME and MOE-treated groups compared to the positive control group. Finally, phytobiotic supplements were shown to improve fish stress tolerance and immune activation for a certain period under stressful conditions or unchanged water, based on the stocking density, dosages of herbs used, and the extent of deterioration of the water quality.

中文翻译：

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植物益生菌掺入饮食对原水中的尼罗河鱼的生长、免疫调节、组织病理学和抗菌作用


植物益生菌是有前途的饮食替代品，但它们在高风险水产养殖条件下的有效性仍未得到充分开发。因此，进行了一项为期 90 天的喂养试验，基于尼罗罗非鱼、Oreochromis niloticus 的膳食补充剂，以及草药提取物，即柠檬香脂 [Melissa officinalis （MOE）]、马郁兰 [Origanum majorana （OME）] 和洋甘菊 [Matricaria chamomilla （MCE）]，换水率为 0%。将治疗组与未用草药处理的组或对照组 [阳性对照 （PC;0% 换水） 和阴性对照 （NC;每天 20% 换水] 进行比较。以放养密度（20 条鱼 m-3：1.8 公斤生物量/m3）养殖鱼类。我们对水进行了理化分析，并评估了鱼的临床反应、生长和免疫反应。此外，然后用致病性 Edwardseilla tarda 菌株攻击补充草药的鱼，并监测死亡率。在第 1 个月和第 2 个月，水参数在允许的范围内。之后，在第 3 个月记录到致命的低溶解氧浓度和最高水平的氨、亚硝酸盐、硝酸盐和 pH 值。在治疗组和对照组进行血液和免疫测定。草药治疗组看起来很健康，但在第 3 个月，嗜睡和食欲下降很明显。一般来说，草药处理的鱼显示出更好的生长性能参数、存活率和对病原菌 E. tarda 的抵抗力，特别是与阳性对照组相比，OME 和 MOE 处理组。 最后，根据放养密度、所用草药的剂量和水质恶化的程度，植物益生菌补充剂被证明可以在压力条件下或水体变化的一段时间内提高鱼类的抗逆能力和免疫激活。