Mystery continues to surround a key mechanism in the early stages of equine pregnancy, say researchers, who believe rapid advancements in molecular biology may eventually allow scientists to solve the riddle.
“Early equine pregnancy shares many features with that of more intensively assessed domestic animals species, but there are also characteristic differences,” Professor Christine Aurich and Dr Sven Budik wrote in the Journal of Animal Science and Biotechnology.
“Some of those are poorly understood” said the pair, from the University of Veterinary Medicine in Vienna.
Descent of the equine conceptus into the uterine lumen occurred at day 5 to 6 after ovulation, but was only possible when the embryo secreted prostaglandin.
They said that although maintenance of equine pregnancy probably involved secretion of a conceptus-derived anti-luteolytic factor, this agent had not been identified.
They said rapid growth, conceptus mobility and the presence of a capsule membrane at the time of maternal recognition of pregnancy, around 12 to 14 days, were required to avoid pregnancy loss.
The researchers, in a review entitled “Early pregnancy in the horse revisited – does exception prove the rule?”, traversed the process and features of the initial stages of equine pregnancy.
They said most of the information available about early equine pregnancy and conceptus development supported the idea of an anti-luteolytic mechanism, which was responsible for maintanence of corpus luteum function beyond the physiological events of the estrous cycle.
The corpus luteum is a hormone-secreting structure that develops in an ovary after an ovum has been discharged. It degenerates after a few days unless pregnancy has begun.
“Despite intensive research, the nature of the embryonic signal for luteostasis in mares remains a mystery,” they said.
“It may be suggested that in the horse, luteolysis is prevented by a more complex conceptus-related mechanism and not only by a single substance.
“The reason why such a mechanism remains undetected until now is unclear. However, it appears feasible that the rapid development of molecular biological methods will eventually allow scientists to solve the riddle.”
Early pregnancy in the horse revisited – does exception prove the rule?
Christine Aurich and Sven Budik
Journal of Animal Science and Biotechnology 2015 6:50 DOI: 10.1186/s40104-015-0048-6
The full paper can be read here.
The research paper was published under an Open-Access License.