Time of embryo transport through the mare oviduct

The objectives of this study were 1) to determine the time of embryo transport through the mare oviduct, 2) to determine whether equine embryos increase in diameter prior to the time of oviductal transport, and 3) to assess the stage of equine embryonic development at the time of oviductal transport. The time of oviductal transport (interval from ovulation to uterine entry) was estimated by collecting embryos from the mare oviduct or uterus at 2-hour intervals from 120 to 168 h postovulation. The time of oviductal transport was 130 to 142 h, since 9 9 embryos were located in the oviduct from 120 to 128 h; 7 14 embryos were in the oviduct and 7 14 embryos were in the uterus from 130 to 142 h; and 13 14 embryos were in the uterus from 144 to 168 h postovulation. Embryos collected during the period of oviductal transport (130 h to 142 h) were not significantly larger (P>0.1) in diameter than embryos collected prior to the period of oviductal transport (162.5+/-3.7 vs 156.7+/-3.1 mum, respectively). During the period of oviductal transport, embryos collected from the uterus were not significantly larger (P>0.1) in diameter than embryos collected from the oviduct (160.7+/-3.2 vs 164.3+/-7.0 mum, respectively). During this same period 12 14 embryos were compact morulae, and 2 14 embryos were blastocysts.