Ultrasonographic findings of the corpus luteum and the gravid uterus during heat stress in dairy cattle

Abstract

The objectives of this study were to assess alterations in, echogenic appearance, size and blood flow in the corpus luteum, the placentomes and the blood flow in umbilical and uterine arteries that heat stress can cause in cooled pregnant dairy cows. Pregnant cows were allocated in two groups and the gravid uteri, along with the ipsilateral corpora lutea were examined during the winter (group W, n = 9) or the summer (group S, n = 10). The grey‐scale ultrasound and colour flow imaging of the corpus luteum and placentome were performed. In addition, the umbilical and uterine artery diameters and haemodynamic parameters in the vessels were calculated. At the time of ultrasonographic examination, cortisol concentrations were higher, and progesterone levels tended to be lower in group S compared to group W. The grey‐scale ultrasound evaluation of corpora lutea and placentomes was lower in group S compared to group W. The diameter of umbilical artery and the blood volume in the vessel were less in group S than in group W. We infer that heat stress affects foetal blood supply and possibly the structure of placentomes and corpora lutea, but it differently affects the blood flow characteristics in the umbilical and uterine arteries.

Climate change and pregnancy complications: From hormones to the immune response

“…Although, the exact contribution of progesterone to thermoregulation is not fully understood, studies in rodents provide evidence that chronic heat stress resulted in reduced concentrations of progesterone ( 14 ). This observation was also confirmed in heat-stressed cattle ( 34 ). However, this effect was no longer evident in rats exposed to heat if challenged for a prolonged period of time ( 16 ).…”

Effect of Season on Ovulatory Response and Reproductive Performance in Noncyclic Lactating Dairy Cows Synchronized with Ovsynch

“…Previous studies revealed that heat stress leading to elevated body temperature directly damages oocyte and also leads to early embryo death (Nanas et al 2021). The results of the previous study clearly demonstrated that the warm season resulted in significantly more pregnancy loss when compared to cool season (Alnimer et al 2009;Hansen 2002;Nanas et al 2021;Wolfenson and Roth 2019). Although a low number of animals in groups might have masked the statistical difference, pregnancy rate on d 62 was relatively 22.2% (a difference of 7.3%) lower in this study.…”

“…Although there was a great percentage of difference in pregnancy loss between warm season (26.7%) and cool season (8%), the lack of statistical difference might have resulted from the small number of animals in this study. Previous studies revealed that heat stress leading to elevated body temperature directly damages oocyte and also leads to early embryo death (Nanas et al 2021). The results of the previous study clearly demonstrated that the warm season resulted in significantly more pregnancy loss when compared to cool season (Alnimer et al 2009;Hansen 2002;Nanas et al 2021;Wolfenson and Roth 2019).…”

“…Global warming causes prolongation of summer periods and heat stress is one of the major reasons for economical losses in the global dairy industry (Nanas et al 2021). Heat stress in the warm season not only impairs the general physiology, welfare, and production but also leads to a reduction in reproductive efficiency (De Rensis et al 2015, Thorton et al 2021.…”

Exogenous L‐arginine administration improves uterine vascular perfusion, uteroplacental thickness, steroid concentrations and nitric oxide levels in pregnant buffaloes under subtropical conditions

“…Instantly, HS impairs foetal blood supply, placental structure and luteal function in bovines (Nanas et al, 2021). In addition, administration of L-Arg improved the uteroplacental development in underfed ewes by reduction of both oxidative stress and endometrial microvessel density (Zhang et al, 2016).…”