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Background <p>In this study, the effects of L-leucine (Leu) on rumen fermentation parameters, rumen epithelium development, amino acid composition, rumen bacterial communities and rumen metabolites in beef cattle were investigated. Twenty-four fattening Angus females of similar initial weight (575.5 ± 22.1&#xa0;kg) were randomly assigned to 2 treatments with 4 replicate pens (3 cattle per pen). They were fed either a basal diet or a basal diet supplemented with 6.0 g L-Leu/100 kg BW/d for 120 d.</p> Results <p>(1) Leu increased the ruminal concentrations of total volatile fatty acid (VFA) (<i>P</i> = 0.017), propionate (<i>P</i> = 0.023), isovalerate (<i>P</i> = 0.001), and branched-chain volatile fatty acid (BCVFA) (<i>P</i> = 0.01) at 4&#xa0;h post-feeding. It also tended to increase acetate (<i>P</i> = 0.083) and decrease the ammonia-N (NH<sub>3</sub>-N) concentration (<i>P</i> = 0.055), but it did not affect ruminal pH (<i>P</i> &gt; 0.1). Leu also increased microbial crude protein (MCP) (<i>P</i> = 0.026) at 4&#xa0;h post-feeding, but decreased MCP at 8&#xa0;h post-feeding (<i>P</i> =&#xa0;0.010). (2) Supplementation with L-Leu increased the ruminal concentrations of phenylalanine (<i>P</i> = 0.011), lysine (<i>P</i> = 0.034), and tyrosine (<i>P</i> = 0.033), while decreasing the cystine concentration (<i>P</i> = 0.010). (3) Leu increased the thickness of the stratum spinosum and basal (<i>P</i> &lt; 0.05), while decreasing the thickness of the stratum granulosum&#xa0;(<i>P</i> &lt;&#xa0;0.05). (4) Leu upregulated the relative mRNA abundance of genes involved in tight junction proteins (<i>P</i> &lt; 0.05) and VFA absorption and metabolism (<i>P</i> &lt; 0.01) in the rumen epithelium. This upregulation was positively correlated with the concentrations ruminal isovalerate and BCVFA (<i>P</i> &lt; 0.01). (5) L-Leu did not affect the diversity and richness of ruminal microbes (<i>P</i> &gt; 0.05), but differential bacterial biomarkers (LEfSe, LDA &gt; 2) were either positively or negatively correlated with ruminal MCP, NH<sub>3</sub>-N, and BCVFA concentrations (<i>P</i> &lt; 0.001). Additionally, differential bacterial metabolites (OPLS-DA, VIP &gt; 1.5) were primarily enriched in the amino acid metabolism pathway and the cofactors and vitamins metabolism pathway (<i>P</i> &lt; 0.05).</p> Conclusions <p>Dietary supplementation with L-Leu altered rumen fermentation parameters and patterns, improved rumen epithelial morphology, and enhanced the expression of genes related to VFA absorption and metabolism in the rumen epithelium of beef cattle.</p>

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Dietary L-leucine supplementation improves ruminal fermentation parameters and epithelium development in fattening Angus beef cattle

  • 期刊论文

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  • 发表日期：

    2025年4月23日

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  • Jishan An,
  • Yu Ge,
  • Huitian He,
  • Hao Ge,
  • Jing Li,
  • Zhiqing Li,
  • Lei Liu,
  • Zuo Wang,
  • Xinyi Lan,
  • Weijun Shen,
  • Anwei Cheng,
  • Fachun Wan

摘要

Background

In this study, the effects of L-leucine (Leu) on rumen fermentation parameters, rumen epithelium development, amino acid composition, rumen bacterial communities and rumen metabolites in beef cattle were investigated. Twenty-four fattening Angus females of similar initial weight (575.5 ± 22.1 kg) were randomly assigned to 2 treatments with 4 replicate pens (3 cattle per pen). They were fed either a basal diet or a basal diet supplemented with 6.0 g L-Leu/100 kg BW/d for 120 d.

Results

(1) Leu increased the ruminal concentrations of total volatile fatty acid (VFA) (P = 0.017), propionate (P = 0.023), isovalerate (P = 0.001), and branched-chain volatile fatty acid (BCVFA) (P = 0.01) at 4 h post-feeding. It also tended to increase acetate (P = 0.083) and decrease the ammonia-N (NH3-N) concentration (P = 0.055), but it did not affect ruminal pH (P > 0.1). Leu also increased microbial crude protein (MCP) (P = 0.026) at 4 h post-feeding, but decreased MCP at 8 h post-feeding (P = 0.010). (2) Supplementation with L-Leu increased the ruminal concentrations of phenylalanine (P = 0.011), lysine (P = 0.034), and tyrosine (P = 0.033), while decreasing the cystine concentration (P = 0.010). (3) Leu increased the thickness of the stratum spinosum and basal (P < 0.05), while decreasing the thickness of the stratum granulosum (P < 0.05). (4) Leu upregulated the relative mRNA abundance of genes involved in tight junction proteins (P < 0.05) and VFA absorption and metabolism (P < 0.01) in the rumen epithelium. This upregulation was positively correlated with the concentrations ruminal isovalerate and BCVFA (P < 0.01). (5) L-Leu did not affect the diversity and richness of ruminal microbes (P > 0.05), but differential bacterial biomarkers (LEfSe, LDA > 2) were either positively or negatively correlated with ruminal MCP, NH3-N, and BCVFA concentrations (P < 0.001). Additionally, differential bacterial metabolites (OPLS-DA, VIP > 1.5) were primarily enriched in the amino acid metabolism pathway and the cofactors and vitamins metabolism pathway (P < 0.05).

Conclusions

Dietary supplementation with L-Leu altered rumen fermentation parameters and patterns, improved rumen epithelial morphology, and enhanced the expression of genes related to VFA absorption and metabolism in the rumen epithelium of beef cattle.