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<p>Largemouth bass (<i>Micropterus salmoides</i>) farming is severely threatened by largemouth bass virus (LMBV), with no effective drugs or commercial vaccines available. β-glucan, a natural immunostimulant, shows promise in enhancing fish disease resistance, but its optimal feeding interval for <i>M. salmoides</i> remains unclear. This study evaluated the effects of dietary β-glucan (0.5&#xa0;g·kg⁻<sup>1</sup> feed) with different feeding intervals on the growth, antioxidant capacity, immune function, intestinal microbiota, and LMBV resistance of <i>M. salmoides</i>. A 4-week feeding trial was conducted with five groups: control (basal diet), F1 (twice daily), F2 (once daily), F3 (once every 2&#xa0;days), and F4 (once every 3&#xa0;days). Results showed all β-glucan groups exhibited higher weight gain rate and specific growth rate, and lower feed conversion ratio than the control, with F2 showing the optimal growth performance. Furthermore, F2 had fewer vacuolated hepatocytes and more intestinal goblet cells, as well as the lowest hepatic malondialdehyde level and the highest serum acid phosphatase and lysozyme activities. Meanwhile, F2 significantly upregulated antiviral genes (<i>ifn-γ</i>, <i>ifn-α3</i>, <i>irf-3</i>) and <i>tgf-β</i>, while downregulating pro-inflammatory cytokines (<i>il-β</i>, <i>tnf-α</i>) in the midgut tissue. Intestinal microbiota analysis revealed that F2 exhibited a higher relative abundance of beneficial <i>Cetobacterium</i> and a lower relative abundance of pathogenic <i>Mycoplasma.</i> LMBV challenge demonstrated F2 had the highest survival rate and lowest viral load. Collectively, once-daily feeding of β-glucan demonstrated the best overall effects among the tested feeding intervals on <i>M. salmoides</i>’ growth performance, antioxidant/immune function, and intestinal microbiota homeostasis, thereby enhancing LMBV resistance. This study provides a scientific basis for the rational application of β-glucan in largemouth bass aquaculture and offers an effective strategy for LMBV disease control, supporting the sustainable development of the industry.</p>

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Effects of dietary algae-derived glucan with optimized feeding intervals on growth, inflammatory response, intestinal microbiota, and resistance of Micropterus salmoides to LMBV infection

  • 期刊论文

  • 发表日期：

    2026年7月28日

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  • Dong chun Li,
  • Qiang Zhu,
  • Chen hua Ni,
  • Chao Liang,
  • Hui Fei,
  • Zhang ying Ye

摘要

Largemouth bass (Micropterus salmoides) farming is severely threatened by largemouth bass virus (LMBV), with no effective drugs or commercial vaccines available. β-glucan, a natural immunostimulant, shows promise in enhancing fish disease resistance, but its optimal feeding interval for M. salmoides remains unclear. This study evaluated the effects of dietary β-glucan (0.5 g·kg⁻1 feed) with different feeding intervals on the growth, antioxidant capacity, immune function, intestinal microbiota, and LMBV resistance of M. salmoides. A 4-week feeding trial was conducted with five groups: control (basal diet), F1 (twice daily), F2 (once daily), F3 (once every 2 days), and F4 (once every 3 days). Results showed all β-glucan groups exhibited higher weight gain rate and specific growth rate, and lower feed conversion ratio than the control, with F2 showing the optimal growth performance. Furthermore, F2 had fewer vacuolated hepatocytes and more intestinal goblet cells, as well as the lowest hepatic malondialdehyde level and the highest serum acid phosphatase and lysozyme activities. Meanwhile, F2 significantly upregulated antiviral genes (ifn-γ, ifn-α3, irf-3) and tgf-β, while downregulating pro-inflammatory cytokines (il-β, tnf-α) in the midgut tissue. Intestinal microbiota analysis revealed that F2 exhibited a higher relative abundance of beneficial Cetobacterium and a lower relative abundance of pathogenic Mycoplasma. LMBV challenge demonstrated F2 had the highest survival rate and lowest viral load. Collectively, once-daily feeding of β-glucan demonstrated the best overall effects among the tested feeding intervals on M. salmoides’ growth performance, antioxidant/immune function, and intestinal microbiota homeostasis, thereby enhancing LMBV resistance. This study provides a scientific basis for the rational application of β-glucan in largemouth bass aquaculture and offers an effective strategy for LMBV disease control, supporting the sustainable development of the industry.