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(NH_3-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,NH_3-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.
基金
supported by the National Key R&D Program(Grant No.2022YFD1301101-1)
National Natural Science Foundation of China(Grant No.32172758)
Key Research and Development Program of Ningxia(Grant No.2024BBF01008)。
