Exposure of Lactating Dairy Cows to Acute Pre-Ovulatory Heat Stress Affects Granulosa Cell-Specific Gene Expression Profiles in Dominant Follicles

Abstract

High environmental temperatures induce detrimental effects on various reproductive processes in cattle. According to the predicted global warming the number of days with unfavorable ambient temperatures will further increase. The objective of this study was to investigate effects of acute heat stress during the late pre-ovulatory phase on morphological, physiological and molecular parameters of dominant follicles in cycling cows during lactation. Eight German Holstein cows in established lactation were exposed to heat stress (28°C) or thermoneutral conditions (15°C) with pair-feeding for four days. After hormonal heat induction growth of the respective dominant follicles was monitored by ultrasonography for two days, then an ovulatory GnRH dose was given and follicular steroid hormones and granulosa cell-specific gene expression profiles were determined 23 hrs thereafter. The data showed that the pre-ovulatory growth of dominant follicles and the estradiol, but not the progesterone concentrations tended to be slightly affected. mRNA microarray and hierarchical cluster analysis revealed distinct expression profiles in granulosa cells derived from heat stressed compared to pair-fed animals. Among the 255 affected genes heatstress-, stress- or apoptosis associated genes were not present. But instead, we found up-regulation of genes essentially involved in G-protein coupled signaling pathways, extracellular matrix composition, and several members of the solute carrier family as well as up-regulation of FST encoding follistatin. In summary, the data of the present study show that acute pre-ovulatory heat stress can specifically alter gene expression profiles in granulosa cells, however without inducing stress related genes and pathways and suggestively can impair follicular growth due to affecting the activin-inhibin-follistatin system.

The Effects of Evaporative Cooling on Folliculogenesis and Ovarian Hormones during the Estrous Cycle of Dairy Holstein Cows during the Summer Months in Saudi Arabia

“…Follicular E2 was much higher in winter than in summer [20]. Other study stated no differences were observed in follicular E2 concentrations between heat-stress and non heat-stressed cows [12]. Heat-stressed cows with lowered E2 during the second half of their cycle [21] or during their entire estrous cycle [11] exhibited reduced pre-ovulatory surges of E2.…”

“…The number of follicles and their functions are affected by HS. Heat stress compromises follicular growth [11] and alters gene expression profiles in the granulosa cells of large pre-ovulatory follicles, which can affect follicular growth [12]. Follicles and oocytes have been damaged by HS, and cows needed 2 -3 estrous cycles to recover from HS effects [13].…”

The effect of chronic, mild heat stress on metabolic changes of nutrition and adaptations in rumen papillae of lactating dairy cows

“…All procedures were approved by the ethics committee of the state government in Mecklenburg-West Pomerania, Germany (LALLF M-V/TSD/7221.3-1.1-074/12), and the data described herein are part of a recently published study (Vanselow et al, 2016). More specifically, 10 German Holstein dairy cows in established second lactation (192 ± 20 DIM) were kept under the same normal environmental conditions in a freestall barn at the Leibniz Institute for Farm Animal Biology (FBN) with daily ad libitum feeding.…”

Post-transfer outcomes in cultured bovine embryos supplemented with epidermal growth factor, fibroblast growth factor 2, and insulin-like growth factor 1

“…Heat stress also contributes to reduced reproductive efficiency by limiting reproductive estrus expression/detection and decreasing conception rate [5]. There are decreases in estradiol-17β concentrations in heat stressed cows, and these reductions in estradiol limit estrus behavior [101,102,106,107]. Fescue toxicosis is another environmental factor that causes infertility in cattle.…”