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<p>Intensified aquaculture practices have increased the vulnerability of farmed fish to infectious pathogens, highlighting nutritional strategies to increase health and reduce antibiotic reliance. Dietary antioxidants such as <i>Nigella sativa</i> (NI) and carvacrol (CA) have shown potential as functional feed additives because of their synergistic effects under bacterial challenge. This study evaluated whether dietary supplementation with NI aqueous extract, CA, or their combination could enhance growth, antioxidant defense, immune function, and disease resistance in <i>Oreochromis niloticus</i> challenged with <i>Aeromonas hydrophila</i>. A total of 120 fish (mean weight 32.28 ± 0.32&#xa0;g) were randomly assigned to four groups with three replicates per group (<i>n</i> = 30 fish/group, 10 fish/replicate): control, NI (10&#xa0;g/kg diet), CA (1&#xa0;g/kg diet), and NI + CA. Fish were fed for eight weeks, followed by experimental infection with <i>A. hydrophila</i>. Growth performance, hematological and biochemical indices, antioxidant enzymes (SOD, GST), lipid peroxidation (MDA), immune parameters (phagocytic activity, myeloperoxidase, total immunoglobulin), and bacterial re-isolation were assessed. Dietary inclusion of NI, CA, or NI + CA significantly improved growth parameters, with the combined group showing the greatest final body weight, weight gain, and specific growth rate, along with a reduced feed conversion ratio. Hematological and biochemical analyses revealed enhanced hemoglobin and leukocyte profiles and favorable modulation of protein, lipid, and glucose metabolism. Supplementation elevated antioxidant enzymes and reduced lipid peroxidation, indicating improved redox balance. Immune assays revealed increased phagocytic activity, myeloperoxidase response, and total immunoglobulin. Following <i>A. hydrophila</i> challenge, the NI + CA group displayed reduced clinical signs, milder lesions, a lower bacterial load, and the highest relative percent survival. Co-supplementation with NI and CA exerted synergistic protective effects across multiple physiological systems, increasing the antioxidant capacity, immune competence, and resistance to bacterial infection in <i>O. niloticus</i>. This study is among the first to demonstrate the synergistic benefits of NI and CA against bacterial challenge in <i>O. niloticus</i>, supporting their application as natural, cost-effective immunostimulants in functional aquafeeds.</p>

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Nigella sativa and carvacrol supplementation modulates physiological, immune, and disease resistance responses in Oreochromis niloticus: evidence of interaction in selected parameters

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年12月1日

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  • Nagwa I. S. Abu-Zahra,
  • Shireen Soliman,
  • Amany M. Ghoniem,
  • Shaimaa Elbaz

摘要

Intensified aquaculture practices have increased the vulnerability of farmed fish to infectious pathogens, highlighting nutritional strategies to increase health and reduce antibiotic reliance. Dietary antioxidants such as Nigella sativa (NI) and carvacrol (CA) have shown potential as functional feed additives because of their synergistic effects under bacterial challenge. This study evaluated whether dietary supplementation with NI aqueous extract, CA, or their combination could enhance growth, antioxidant defense, immune function, and disease resistance in Oreochromis niloticus challenged with Aeromonas hydrophila. A total of 120 fish (mean weight 32.28 ± 0.32 g) were randomly assigned to four groups with three replicates per group (n = 30 fish/group, 10 fish/replicate): control, NI (10 g/kg diet), CA (1 g/kg diet), and NI + CA. Fish were fed for eight weeks, followed by experimental infection with A. hydrophila. Growth performance, hematological and biochemical indices, antioxidant enzymes (SOD, GST), lipid peroxidation (MDA), immune parameters (phagocytic activity, myeloperoxidase, total immunoglobulin), and bacterial re-isolation were assessed. Dietary inclusion of NI, CA, or NI + CA significantly improved growth parameters, with the combined group showing the greatest final body weight, weight gain, and specific growth rate, along with a reduced feed conversion ratio. Hematological and biochemical analyses revealed enhanced hemoglobin and leukocyte profiles and favorable modulation of protein, lipid, and glucose metabolism. Supplementation elevated antioxidant enzymes and reduced lipid peroxidation, indicating improved redox balance. Immune assays revealed increased phagocytic activity, myeloperoxidase response, and total immunoglobulin. Following A. hydrophila challenge, the NI + CA group displayed reduced clinical signs, milder lesions, a lower bacterial load, and the highest relative percent survival. Co-supplementation with NI and CA exerted synergistic protective effects across multiple physiological systems, increasing the antioxidant capacity, immune competence, and resistance to bacterial infection in O. niloticus. This study is among the first to demonstrate the synergistic benefits of NI and CA against bacterial challenge in O. niloticus, supporting their application as natural, cost-effective immunostimulants in functional aquafeeds.