The first aim of this study was to determine the influence of the procedures [hormonal treatments for fixed time artificial insemination (FTAI) versus insemination at spontaneous oestrus (SEAI)] on several sequential inseminations (AI). A second aim was to determine the influence of some intrinsic and extrinsic factors and their interactions, including characteristics of the animals such as age, season, farm, sire, and AI technician on the response to both procedures. A retrospective analysis was performed from a data base of 120.807 AIs of healthy cows with at least 40–70 days post‐partum at first service. Overall, FTAI achieved slighter greater pregnancy rates than insemination after detected oestrus. The second AI seems to be a key insemination as effects of sire and technician were greater than in the following ones. The use of FTAI or SEAI in one AI did not affect the results of the following AIs, regardless if FTAI or SEAI procedures were used in that AI. Technician had greater variation than sire or farm on final pregnancy rate. The results of each sire for pregnancy rate varied according to the type of insemination, with sires achieving greater results with one or other procedure. Pregnancy rate was positively related to the days in milk in the first two AIs. Results were greater in autumn than in spring services.

中文翻译：

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奶牛在检测到发情后或在固定时间进行人工授精的怀孕概率：大规模农场研究中内在和外在因素的影响

本研究的第一个目的是确定程序 [固定时间人工授精 (FTAI) 与自然发情时授精 (SEAI) 的激素治疗] 对几个连续授精 (AI) 的影响。第二个目的是确定一些内在和外在因素及其相互作用的影响，包括动物的特征，如年龄、季节、农场、种畜和 AI 技术人员对这两种程序的反应。对 120.807 头产后至少 40-70 天的健康奶牛的 AI 数据库进行了回顾性分析。总体而言，在检测到发情后，FTAI 的妊娠率略高于人工授精。第二个人工智能似乎是一个关键的授精，因为父亲和技术员的影响比下面的要大。在一个 AI 中使用 FTAI 或 SEAI 不会影响以下 AI 的结果，无论该 AI 中是否使用了 FTAI 或 SEAI 程序。技术人员在最终妊娠率上的差异比公猪或农场更大。每个公牛的受孕率结果根据授精类型而有所不同，公牛通过一种或其他程序获得更好的结果。在前两个 AI 中，妊娠率与牛奶中的天数呈正相关。秋季服务的结果比春季服务要好。在前两个 AI 中，妊娠率与牛奶中的天数呈正相关。秋季服务的结果比春季服务要好。在前两个 AI 中，妊娠率与牛奶中的天数呈正相关。秋季服务的结果比春季服务要好。