Department of Animal Science, Institute of Agriculture, University of Tennessee, Knoxville, TN 37996, USA.
Department of Animal Science, Pregnancy and Developmental Programming Area of Excellence, Texas A & M University, College Station, TX 77843, USA.
J Anim Sci. 2022 Jul 1;100(7). doi: 10.1093/jas/skac100.
The overarching aim was to examine the relationship of rectal temperature at fixed time artificial insemination (FTAI) on pregnancy outcomes in a typical breeding season with expected pregnancy rates approaching 50% using Bos indicus and Bos taurus cattle. This represents a continuum of steps to test the hypothesis that elevated body temperature at or around insemination is functionally important to maximize pregnancy outcomes. Rectal temperature of Bos indicus cattle at FTAI ranged from 37.0 to 40.9 °C; 60.6% were hyperthermic. Positive factors impacting pregnancy outcomes were rectal temperature at FTAI, body condition, and estrus patch scores. Rectal temperature at FTAI was positively associated with pregnancy outcomes (P < 0.0001); per each 1 °C increase pregnancy odds increased 1.9 times (95% CI: 1.4 to 2.6). Highest pregnancy outcomes occurred with rectal temperatures exceeding 40 °C (P = 0.0004). Rectal temperature before FTAI in Bos taurus cattle ranged from 37.8 to 41.8 °C; 43.3% were hyperthermic. Factors impacting pregnancy were rectal temperature at FTAI, estrus activity, parity, and ambient conditions on day of FTAI. Rectal temperature of Bos taurus cattle at FTAI was positively associated with pregnancy (P = 0.0286); odds increased 1.45 times (95% CI: 1.0 to 2.0) per each 1 °C increase. Highest pregnancy outcomes occurred with rectal temperatures at FTAI exceeding 40 °C (P = 0.057). Moreover, positive relationship of rectal temperature at FTAI to pregnancy persisted in estrual females (71.25% of total; P = 0.0408; OR 1.5; 95% CI: 1.0 to 2.2). Mindful that 1) elevated temperatures observed in Bos indicus and Bos taurus cattle directly promote meiotic resumption of the oocyte in vitro and that 2) in vivo hyperthermia alters intrafollicular components which others have shown to potentiate ovulation and promote meiotic resumption, it is biologically plausible that an acute elevation in body temperature at or around time of insemination is functionally important to maximize pregnancy outcomes.
本研究的主要目的是在一个典型的繁殖季节，使用印度瘤牛和普通牛，检查固定时间人工授精（FTAI）时直肠温度与妊娠结局的关系，预计妊娠率接近 50%。这是一系列步骤中的一步，旨在检验这样一个假设，即在授精时或授精前后体温升高对最大限度地提高妊娠结局具有重要的功能作用。FTAI 时印度瘤牛的直肠温度范围为 37.0 至 40.9°C；60.6%的牛体温升高。对妊娠结局有积极影响的因素包括 FTAI 时的直肠温度、体况和发情斑评分。FTAI 时的直肠温度与妊娠结局呈正相关（P < 0.0001）；每升高 1°C，妊娠几率增加 1.9 倍（95%CI：1.4 至 2.6）。直肠温度超过 40°C 时，妊娠结局最高（P = 0.0004）。FTAI 时普通牛的直肠温度范围为 37.8 至 41.8°C；43.3%的牛体温升高。影响妊娠的因素包括 FTAI 时的直肠温度、发情活动、胎次和 FTAI 当天的环境条件。FTAI 时普通牛的直肠温度与妊娠呈正相关（P = 0.0286）；每升高 1°C，几率增加 1.45 倍（95%CI：1.0 至 2.0）。直肠温度超过 40°C 时，妊娠结局最高（P = 0.057）。此外，FTAI 时直肠温度与妊娠的正相关关系在发情雌性动物中仍然存在（占总数的 71.25%；P = 0.0408；OR 1.5；95%CI：1.0 至 2.2）。考虑到 1）在体外观察到的印度瘤牛和普通牛的高温直接促进卵母细胞减数分裂恢复，以及 2）体内发热改变了卵泡内成分，其他人已经表明这可以增强排卵并促进减数分裂恢复，因此在授精时或授精前后体温升高对最大限度地提高妊娠结局具有重要的功能作用，这在生物学上是合理的。
