[目的]探究乳肉兼用牛发情期牛乳中孕酮与乳汁成分的变化,揭示其调控机制。[方法]选取65 头健康乳肉兼用牛,采用酶联免疫吸附法（ELISA）检测乳肉兼用牛发情期孕酮浓度,结合全自动乳成分分析仪检测乳脂率、乳蛋白率及乳糖含量。通过线性混合模型、多元回归及协方差分析（ANCOVA）解析孕酮与乳汁成分的关联性,并评估胎次与泌乳阶段的调节效应。[结果]发情期孕酮呈现显著动态变化,峰值期为发情前48 h,发情日骤降,乳脂率与乳蛋白率同步波动,与孕酮呈强正相关。乳糖含量变化幅度非常小,与孕酮相关不显著。2 胎奶牛孕酮-乳脂率相关性较多胎高23.60%,泌乳中期相关性最强。[结论]孕酮通过调控乳腺代谢活动显著影响乳脂与乳蛋白合成,其效应受胎次和泌乳阶段调节。研究结果为靶向营养干预及繁殖管理提供关键时间窗口与科学依据。

[Objective] To investigate the changes in progesterone and milk composition traits in dual-purpose cattle during estrus, reveal their regulatory mechanisms, and provide a scientific basis for optimizing breeding management.[Method] Sixty-five healthy dual-purpose cattle were selected. Progesterone concentrations during the estrous cycle were measured using enzyme-linked immunosorbent assay （ELISA）,while milk fat rate,milk protein rate, and lactose content were determined with a fully automatic milk composition analyzer.The associations between progesterone and milk components were analyzed via linear mixed models （LMMs）, multiple regression, and analysis of covariance （ANCOVA）, with parity and lactation stage evaluated as regulatory factors.[Result] Progesterone exhibited significant dynamic changes during estrus, peaking at 48 hours pre-estrus and sharply declining on the day of estrus. Milk fat and protein rates fluctuated synchronously, showing strong positive correlations with progesterone （r>0.30,p< 0.05）.Lactose content varied minimally, with no significant association to progesterone （r < 0.1,p> 0.05）. The progesterone-milk fat correlation was 23.60% higher in second-parity cows than in multiparous cows, with the strongest correlation observed during mid-lactation（r=0.42,p< 0.01）.[Conclusion] Progesterone significantly influences milk fat and protein synthesis by regulating mammary gland metabolic activity, with effects modulated by parity and lactation stage. These findings provided a critical time window and scientific basis for targeted nutritional interventions and reproductive management.