Early embryo losses, progesterone and pregnancy associated glycoproteins levels during summer heat stress in dairy cows. (May 2021)

• Record Type: Journal Article
• Authors: Nanas, Ioannis; Chouzouris, Thomas-Markos; Dovolou, Eleni; Dadouli, Katerina; Stamperna, Konstantina; Kateri, Ilektra; Barbagianni, Mariana; Amiridis, Georgios S.
• Is Part Of: Journal of thermal biology. Volume 98(2021)
• Publication Date: 2021-05
• Subjects: Heat stress -- Progesterone -- Pregnancy associated glycoproteins -- Embryo death -- Cattle; THI Temperature Humidity Index -- PAG Pregnancy Associated Glycoproteins -- AI Artificial Insemination; Thermobiology -- Periodicals; Temperature -- Periodicals; Biology -- Periodicals; Thermobiologie -- Périodiques; Thermobiology; Periodicals; 571.46
• DOI: 10.1016/j.jtherbio.2021.102951
• Languages: English
• ISSNs: 0306-4565

Abstract

Abstract: 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. Highlights: In dairy cows, during the summer, the likelihood for conception failure is 13 to 19% higher compared to the winter. In days 24 to 31 of cattle pregnancies, more embryo losses occur in summer than in winter. In days 33 to 36 of pregnancy, placental PAG production is increased in summer compared to winter. In early pregnancies of dairy cows during the hot months, progesterone secretion is seriously compromised.