More dairy farms (up to more than one in four in some countries) are equipped with automatic milking systems (AMS) worldwide. Because of the positive impacts of grazing, e.g., on animal welfare or on production costs, numerous researchers have published papers on the combination of AMS with grazing. However, pasture-based AMS usually causes a reduction in milking frequency (MF) compared to indoors systems. The objectives of this meta-analysis were to review publications on the impacts of pasture-based AMS on MF and mitigation strategies. First, data from 43 selected studies were gathered in a dataset including 14 parameters, and on which a Principal Component Analysis (PCA) was performed, leading to the description of four clusters summarizing different management practices. Multiple pairwise comparisons were performed to determine the relationship between the highlighted parameters of MF on milk yield (MY). From these different analyses, the relationship between MF and MY was confirmed, the systems, i.e., Clusters 1 and 2, that experienced the lowest MF also demonstrated the lowest MY/cow per day. In these clusters, grazed grass was an essential component of the cow’s diet and low feeding costs compensated MY reduction. The management options described in Clusters 3 and 4 allowed maintenance of MF and MY by complementing the cows’ diets with concentrates or partial mixed ration supplied at the AMS feeding bin or provided at barn. The chosen management options were closely linked to the geographical origin of the papers indicating that other factors (e.g., climatic conditions or available grasslands) could be decisional key points for AMS management strategies.

中文翻译：

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系统评价和荟萃分析：结合自动挤奶系统，确定影响奶牛挤奶频率的因素。

全球范围内，越来越多的奶牛场（在某些国家中多达四分之一）配备了自动挤奶系统（AMS）。由于放牧对动物福利或生产成本的积极影响，许多研究人员发表了有关AMS与放牧结合的论文。但是，与室内系统相比，基于牧场的AMS通常会导致挤奶频率（MF）降低。这项荟萃分析的目的是审查有关基于牧场的AMS对MF和缓解策略的影响的出版物。首先，将来自43项选定研究的数据收集到包括14个参数的数据集中，并对其进行了主成分分析（PCA），从而形成了对四个分类的概述，总结了不同的管理实践。进行多次成对比较以确定MF突出显示的参数与产奶量（MY）之间的关系。从这些不同的分析中，证实了MF和MY之间的关系，经历最低MF的系统（即群集1和2）也显示出每天最低的MY /牛。在这些集群中，放牧的草是母牛日粮中不可或缺的组成部分，较低的饲喂成本弥补了MY降低的风险。第3组和第4组中描述的管理选项通过在AMS饲喂箱中或在谷仓中提供的浓缩或部分混合日粮补充奶牛的日粮来维持MF和MY。选择的管理选项与文件的地理来源紧密相关，表明其他因素（例如，