Intrauterine movement of the early conceptus in barren and postpartum mares.

This study investigates the intrauterine mobility patterns of the embryonic vesicle in barren and postpartum mares, using ultrasonography. It found no significant differences between the two groups in terms of vesicle location changes or time spent in each horn of the uterus. In an additional experiment, the rate of movement of the embryonic vesicle was measured at an average rate of 3.4 mm/min.

Study on Vesicle Mobility Patterns

• The main objective of the study was to compare intrauterine mobility patterns of the embryonic vesicle (a hollow structure containing the embryo) in barren (nonpregnant) and postpartum (after childbirth) mares. The study was conducted over three days (days 12, 13, 14) post fertilization.
• Through the use of an ultrasound instrument, the location of the vesicle within the uterus (whether in the left horn, right horn or body of the uterus) was recorded every five minutes during six two-hour trials for each group (barren and postpartum).
• The vesicle was found to move from one horn to the other 1.1 times per two-hour trial on average, with no significant differences found between barren and postpartum mares in the frequency of these movements or the amount of time spent in each horn.

Observations on Postpartum Mares

• In postpartum mares, the study found no differences in the number of location changes or time spent in the previously pregnant horn (gravid horn) and the non-pregnant horn (nongravid).
• Previous reports had suggested frequent attachment of the vesicle to the nongravid horn, but this was not found to relate to any difference in mobility or time spent in the nongravid horn during the period of high intrauterine mobility examined in this study.

Estimation of Embryonic Vesicle Movement Rate

• The second experiment of the study estimated the rate of movement of the embryonic vesicle within the body of the uterus between days 12 to 14, based on fixed points of reference like the cranial end of the cervix and uterine cysts.
• The average movement rate was estimated at 3.4 mm/min, with a range of 0-14 mm/min.
• Using time-lapse photography at one-minute intervals, an instance of vesicle movement was documented where the vesicle approached a cyst, formed an indentation, moved over the cyst, and continued moving in the same direction.