EARLY EMBRYONIC DEVELOPMENT AND MATERNAL RECOGNITION OF PREGNANCY IN CAMELIDS: A REVIEW

Maternal recognition of pregnancy (MRP) is a biological process that allows a female to recognize the presence of a conceptus and sustain the lifespan of the corpus luteum (CL). In-depth studies on MRP have been sparked by the impact of early pregnancy loss on productivity in various large animal domestic species. Reproductive studies in camelids are limited and our knowledge of MRP in this species has lagged behind compared to other domestic species. MRP in camelids seems to be driven primarily by estrogen secretion from the hatched blastocyst and possibly other mechanisms related to elongation. The presence of the conceptus blocks the induction of endometrial COX-2 expression resulting in attenuation of PGF2α and rescue of the CL. A substance such as IFNτ has not been identified in camelids. Oxytocin does not appear to play a major contributing role in this process. Embryos migrate to the left uterine horn in order for luteal function to be maintained. Studies thus far have not shown a difference between the left and right uterine horn related to histological changes and estrogen receptor expression. More recently investigation of expression levels of genes previously identified as conceptus regulated genes in the endometrium of other domestic animals has been evaluated in camels. The objectives of the current review are to present the current state of our knowledge on MRP in camelids and discuss early embryonic development in this species and how it may relate to MRP.