|Bridges, G -|
|Day, M -|
|Cruppe, L -|
Submitted to: Journal of Animal Science
Publication Type: Review Article
Publication Acceptance Date: November 19, 2012
Publication Date: January 10, 2013
Citation: Bridges, G.A., Day, M.L., Geary, T.W., Cruppe, L.H. 2013. Deficiencies in the uterine environment and failure to support embryo development. Journal of Animal Science. 91:3002-3013. Interpretive Summary: Many factors affect pregnancy success in cows. One of the greatest limitations of may be preparation of the cow’s uterus for pregnancy. This review focuses primarily on the role that ovarian steroids play in preparing the uterus for pregnancy. High levels of estradiol in the blood before ovulation and progesterone after ovulation are necessary to prepare the uterus for pregnancy. It is known that low blood levels of estradiol before ovulation create uterine deficiencies that prevent pregnancy, but the mechanism is not yet known. Low blood levels of progesterone during early pregnancy result in decreased nutrient availability for the developing embryo. These changes retarded embryo development and result in embryo death. Future research needs to focus on these limitations to clarify their roles.
Technical Abstract: Pregnancy failure in livestock can result from failure to fertilize the oocyte or embryonic loss during gestation. Although fertilization failure occurs, embryonic mortality has a greater contribution to pregnancy failure. The focus of this review is on cattle and factors affecting, and mechanisms related to, uterine insufficiency for pregnancy. A variety of factors contribute to embryonic loss and it may be exacerbated in certain animals, such as high-producing lactating dairy cows and in some cattle in which estrous synchronization and timed AI was performed, due to reduced concentrations of reproductive steroids. Recent research in beef cows induced to ovulate immature follicles and lactating dairy cows suggest that deficient uterine function is the primary factor responsible for infertility in these animals. Failure to provide adequate concentrations of estradiol before ovulation results in prolonged effects on expression and localization of uterine genes and proteins that participate in regulating uterine functions during early gestation. Furthermore, progesterone concentrations during early gestation affect embryonic growth, interferon-tau production, and uterine function. Therefore, an inadequate uterine environment induced by insufficient steroid concentrations before and after ovulation could cause early embryonic death either by failing to provide an adequate uterine environment for recognition of embryo signaling, adhesion, and implantation, or by failing to support appropriate embryonic growth which could lead to decreased conceptus size and malfunction of the process of maternal recognition of pregnancy.