Mare Follicle Size Ovulation

50 of mares ovulate 24 hours before the end of heat 30 ovulate 48 hours before the end of heat some mares may come into.

Mare follicle size ovulation. The trick to effective breeding is knowing precisely when a mare is ready to ovulate. Traditionally follicle size was used to make this determination. This growth ultimately peaks and holds steady for about a. Indications of impending ovulation in the mare.

Follicles of diameters greater than or equal to 1 2 inches 3 cm were considered to be highly likely to ovulate in the next 48 hours. Double follicles may ovulate at a smaller size and may feel like a single follicle on palpation. Owners who want to schedule breeding can have a veterinarian examine the mare by ultrasound or palpation to check the progress of follicles as they form and mature on the mare s ovaries. Time to ovulation is variable 3 10 days and depends on the stage of the mare s current follicular wave and on the size and character of follicles at the time of pgf 2α administration.

Estrus duration is usually three to seven days. The size of the follicle the day before ovulation is detected is commonly 35 to 45 mm in diameter but mares can ovulate much smaller follicles less than 30 mm or larger follicles with normal fertility. The mare will come into estrus 2 5 days after administration of pgf 2α. Ideally the mare is bred a few hours before ovulation so that the sperm will be already in the fallopian tube when the egg is released.

Small follicle size at ovulation may be a cause of apparent infertility. A flattening effect to the top of the follicle may be seen when gentle pressure is applied with the ultrasound probe once the follicle starts to soften prior to ovulation. The maximal diameter of the follicle was 43 4 mm. The follicle that ovulated at the end of estrus develops into a structure call the corpus luteum cl.

By day 16 of the mare s cycle the developing follicle has reached the size at which it secretes enough hormone to bring on the external characteristics of heat. In 89 of the follicles the round shape became more irregular before ovulation. If the mare is not pregnant the. The preovulatory follicle grew 3 mm a day up to 2 days before ovulation.

Follicle growth pattern mccue explained that a mare s dominant follicle typically increases in diameter by 2 7 3 mm a day during estrus. The mare enters diestrus following ovulation and the end of estrus. By tracking changes in the size and shape of a follicle the veterinarian can make a fairly accurate prediction of when the mare will ovulate release the. Ovulation most frequently occurs 24 to 48 hours prior to the end of estrus.