The objective of this retrospective study was to investigate the prevalence of pregnancy loss (PL; between 28–110 pregnancy days) and its relationship with factors: farm, year (2015–2018), season, artificial insemination (AI)-rank, parity, AI-type (fixed-time vs. oestrus-AI), previous PL, days in milk (DIM), fixed-time-AI protocol, AI-technician, bull, and semen-type (sexed vs. conventional). Data of 19,437 Holstein cattle AIs from eight Spanish farms were studied. Overall conception rate was 34.3% (6696/19,437) and PL 12.3% (822/6696). The PL was more likely to occur in primiparous (10.8%, odds ratio (OR) = 1.35; p = 0.04) and multiparous (15.3%; OR = 2.02, p < 0.01) than in heifers (PL = 6.9%, reference). Pregnancies achieved with AI after observed oestrus and natural breedings were associated with less PL than pregnancies after fixed-time-AI (12.7 vs. 11.9%; OR = 0.12, p = 0.01). First AIs related to higher PL than ≥2nd AIs (PL = 13.8% vs. 11.2; OR = 0.73, p < 0.01). The factors season, fixed-time-AI protocol, DIM, bull, AI-technician, or type of semen were not significantly associated with PL. Therefore, farmers and consultants should adapt their preventive strategies relating to PL, particularly, to the parity of the cattle.

中文翻译：

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荷斯坦奶牛的妊娠损失（妊娠28-110天）：一项回顾性研究。

这项回顾性研究的目的是调查妊娠流失的发生率（PL；妊娠28-110天之间）及其与以下因素的关系：农场，年份（2015-2018年），季节，人工授精（AI）等级，均等，AI型（固定时间与发情AI），以前的PL，牛奶天数（DIM），固定时间AI协议，AI技术员，公牛和精液类型（性与常规）。研究了来自八个西班牙农场的19,437头荷斯坦牛AIs的数据。总体受孕率为34.3％（6696 / 19,437）和PL为12.3％（822/6696）。PL更有可能以初产（10.8％，比值比（OR）= 1.35; p = 0.04）和多胎（15.3％; OR = 2.02，p<0.01）比小母牛（PL = 6.9％，参考）。观察到的发情期和自然繁殖后，通过AI进行的妊娠与固定时间AI进行的妊娠相比，PL的发生率较低（12.7对11.9％； OR = 0.12，p = 0.01）。第一个AI与≥2个AI更高的PL相关（PL = 13.8％vs. 11.2; OR = 0.73，p <0.01）。季节，固定时间AI协议，DIM，公牛，AI技术员或精液类型与PL的相关性不明显。因此，农民和顾问应调整其与PL有关的预防策略，尤其是与牛的同等水平。