Characterization of Blood Metabolites and the Uterine Microbiota in Estrus Simmental Cattle

Accurate oestrus detection is critical for optimizing reproductive efficiency in beef cattle, yet the underlying metabolic and microbial mechanisms remain poorly understood, particularly in Simmental cattle. To address this gap, we employed an integrated metabolomics and microbiome approach to systematically characterize blood metabolic profiles and uterine microbiota dynamics during oestrus. The results revealed significantly elevated serum levels of total protein, albumin, glucose and insulin-like growth factor-1 (IGF-1) (P<0.01) during oestrus, and metabolomics revealed 258 differentially abundant metabolites enriched primarily in amino acid and lipid metabolism pathways. Cervical microbiome analysis revealed Firmicutes and Bacteroidetes as the dominant bacterial phyla, whereas fungal Ascomycota presented significantly increased relative abundance (78.38% vs 67.20%) with reduced α diversity (P<0.05) during estrus. Functional prediction analysis further revealed significant enrichment of bacterial energy metabolism pathways (TCA cycle; q<0.01), strong positive correlations between Bacteroides and bile acids (r>0.6, P<0.01), and significant associations between Candida and lipid metabolites. These findings establish a 'microbiota‒metabolite‒host' interaction network specific to oestrus in Simmental cattle, providing novel theoretical foundations and potential biomarkers for optimizing reproductive management in cattle herds.精准的发情检测对优化肉牛繁殖效率至关重要，但相关代谢与微生物组机制仍未得到充分阐明，在西门塔尔牛（Simmental cattle）中这一问题尤为突出。为填补这一研究空白，本研究采用代谢组学（metabolomics）与微生物组学（microbiome）联合分析策略，系统表征了发情期血液代谢组特征与子宫微生物群的动态变化。研究结果显示，发情期血清总蛋白、白蛋白、葡萄糖及胰岛素样生长因子-1（insulin-like growth factor-1，IGF-1）水平显著升高（P<0.01）；代谢组学分析共鉴定出258个差异丰度代谢物，主要富集于氨基酸代谢与脂质代谢通路。宫颈微生物组分析显示，厚壁菌门（Firmicutes）与拟杆菌门（Bacteroidetes）为优势细菌门类；发情期子囊真菌门（Ascomycota）的相对丰度显著升高（78.38%相较于67.20%），而α多样性显著降低（P<0.05）。功能预测分析进一步揭示，细菌能量代谢通路（三羧酸循环，TCA cycle）显著富集（q<0.01）；拟杆菌属（Bacteroides）与胆汁酸呈强正相关（r>0.6，P<0.01）；念珠菌属（Candida）与脂质代谢物存在显著关联。本研究构建了西门塔尔牛发情特异性的“微生物群-代谢物-宿主”互作网络，为肉牛群的繁殖管理优化提供了全新的理论基础与潜在生物标志物。