Comprehensive study on dynamics of early embryonic development in Marwari mares

Abstract

Horse is a seasonal breeder with reproductive activity being associated with long days, i.e. occurring in spring and early summer. Early equine pregnancy shares many features with that of more intensively assessed domestic animals species, but there are also characteristic differences. In mares, early diagnosis of pregnancy can be done due to the spherical shape. The ultrasonic visualization of conceptus is possible from day 9 of equine pregnancy. In spite of numerous, substantial advances in equine reproduction, many stages of embryonic and foetal morphological development are poorly understood, with no apparent single source of comprehensive information. Hence, in the present study we aimed at studying the dynamics of early embryonic developments in equines, particularly for Marwari breed of horses. The results from the current study revealed that, embryonic vesicles (EV) were first observed on 11th day, fixation occurred after 16.25±0.25 days of ovulation, EV lost spherical shape on 15.83±0.38 days, became oval on 17–18th days and irregular on 19–20th days. Heartbeat, detection of allantoic sac, start of foetal ascent, start of foetal descend and end of foetal descend were detected on 23.91±0.41, 23.58±0.35, 38.66±0.28, 40.66±0.33 and 47.33±0.28 days, respectively. In conclusion, early detection of embryonic vesicles and continuous changes observed in conceptus structure indicate positive pregnancy, viability of embryo and are much beneficial in preventing economical loss of equine owner and stable farm.