One of the reasons why fertility of cows decline during the summer is because the summer heat stress negatively affects the secretion of prostaglandins in the oviducts, causing hormone imbalances, according to a research group of the Okayama University Graduate School of Environmental and Life Science.
Professor Kiyoshi Okuda who heads the research group said the findings will be helpful in analyzing the causes of oviduct malfunction and searching ways to improve the conception rates.
Peristaltic movements of oviducts, which are the forces leading to transportation of early embryos to the uterus, are affected by secretion of two types of hormone-like substance prostaglandin – prostaglandin E2(PGE2) and prostaglandin F2α(PGF2α). The group found out that the secretion of PGE2 increases in a high-temperature environment, while the secretion of PGF2α remains the same, thus triggering hormonal imbalance.
In an experiment using the epithelial cells of a cow’s oviduct, the group confirmed that PGE2 production increased at 40.5 degrees centigrade, a higher degree than the normal body temperature. They also examined the oviductal tissues and found out that the amount of enzyme which forms PGE2 was higher in the summer than in the winter, and that the heat shock protein 90 which activates the enzyme increases at high temperatures.
The overall results suggest that the heat shock protein 90 upsets the secretion of prostaglandins and reduces smooth muscle movement of the oviduct, which in turn could decrease the transport of embryo through the oviduct, the group said.
(July 19, 2013)