Nanas Ioannis, Chouzouris Thomas-Markos, Dovolou Eleni, Dadouli Katerina, Stamperna Konstantina, Kateri Ilektra, Barbagianni Mariana, Amiridis Georgios S
Clinic of Obstetrics & Reproduction, Veterinary Faculty, University of Thessaly, Karditsa, Greece.
Clinic of Obstetrics & Reproduction, Veterinary Faculty, University of Thessaly, Karditsa, Greece; Laboratory of Reproduction, Faculty of Animal Science, University of Thessaly, Greece.
J Therm Biol. 2021 May;98:102951. doi: 10.1016/j.jtherbio.2021.102951. Epub 2021 Apr 8.
Objectives of this study were to characterize the effects of heat stress on pregnancy associated glycoproteins (PAG) and progesterone and its involvement in embryo survival. In trial 1, blood samples collected from days 29 to 36 post insemination were examined for the comparison of PAG concentrations between winter (n = 3721) and summer (n = 2388). In trial 2, embryo losses were assessed in winter (n = 144) and in summer (n = 133), in days 31 or 32 of pregnancy. Pregnancy diagnosis was carried out by ultrasonography on days 24 or 25, and it was repeated a week later; in the second occasion PAG concentration was also determined. In trial 3 the PAG and progesterone concentrations were assessed in days 33 to 36 in winter and summer. In trial 1 PAG levels did not differ between winter and summer, the conception rate and the proportion of uncertain pregnancies were higher in winter than summer. The likelihood of pregnancy was 10 to 15% higher in winter. In trial 2, the embryo death rate was higher in summer, but the PAG levels of cows that had embryo loss in summer were higher than those in winter. In both seasons, lower PAG levels were associated with higher risk of pregnancy loss, while embryo death was five times more likely to occur in summer than in winter and lower PAG concentrations were positively associated with higher risk of embryo loss. In trial 3, mean PAG levels were higher and of progesterone were lower during the summer than during the winter. We infer that despite the devastating effects of heat stress on cows' fertility, those early embryos that survive under continuous heat stress can form a well-functioning placenta; hence, the high embryo mortality rate observed during the summer months could be mainly attributed to luteal insufficiency.
本研究的目的是确定热应激对妊娠相关糖蛋白（PAG）和孕酮的影响及其与胚胎存活的关系。在试验1中，采集授精后第29至36天的血样，以比较冬季（n = 3721）和夏季（n = 2388）之间的PAG浓度。在试验2中，评估冬季（n = 144）和夏季（n = 133）妊娠第31或32天的胚胎损失情况。在妊娠第24或25天通过超声进行妊娠诊断，并在一周后重复进行；第二次诊断时还测定了PAG浓度。在试验3中，评估冬季和夏季第33至36天的PAG和孕酮浓度。在试验1中，冬季和夏季的PAG水平没有差异，冬季的受孕率和不确定妊娠的比例高于夏季。冬季怀孕的可能性高出10%至15%。在试验2中，夏季的胚胎死亡率较高，但夏季发生胚胎损失的奶牛的PAG水平高于冬季。在两个季节中，较低的PAG水平与较高的妊娠损失风险相关，而夏季胚胎死亡的可能性是冬季的五倍，较低的PAG浓度与较高的胚胎损失风险呈正相关。在试验3中，夏季的平均PAG水平较高，孕酮水平较低。我们推断，尽管热应激对奶牛的繁殖力有毁灭性影响，但那些在持续热应激下存活的早期胚胎可以形成功能良好的胎盘；因此，夏季观察到的高胚胎死亡率可能主要归因于黄体功能不全。
