Reproduction
The ultrasound device is used to examine the mares rectally. The thickness of the uterine wall, the presence of any cysts and especially the amount of edema in the uterus are examined. The uterine edema gives an indication of where the mare is in the cycle. The edema is at its maximum 1 to 2 days before ovulation.
The ovaries contain (maturing) follicles. There is usually 1 dominant large follicle that will mature and eventually ovulate: this follicle must be monitored. The maximum size of the follicle varies per breed and per mare. Does the follicle change shape and consistency? Then there is a good chance that ovulation will take place within 12 to 48 hours.
It is important to know how the sperm is transported. Fresh sperm has a lifespan of 48 hours, refrigerated sperm 24-48 hours and frozen sperm has a lifespan of 12 hours.
A mare can be inseminated with (cooled) fresh semen just before ovulation. According to the standard rules, the mare is in good heat, has a wide and flaccid cervix (= uterine mouth), reduced edema of the uterus, follicle size of 40-50 mm and the follicle is soft with possible shape changes. Insemination with frozen semen must take place just before or just after ovulation. Therefore, these mares are preferably scanned 2 to 3 times a day, depending on the possibilities.
The mare is checked 14 to 16 days after insemination. The fetus must be found in the uterus. A search is also made for twins: twin pregnancies should be avoided! The complications in horses are too great to take the risk, the chance of a good delivery with two healthy foals is very small.