Regardless of what day of gestation you check for twins, it is much easier to reduce a twin before they become fixed at Day 17 of gestation. If you consistently check mares at Day 14, at some point you will miss a younger twin that is 12 or 13 days old and too small to be visualized. This author prefers to check mares on Day 15 or 16 since the twin should be 14 or 15 days old. All horses should be examined for twins with transrectal ultrasound. They are uncommon in Quarter horses (five to 10 percent). Twins are more common in Thoroughbreds (25 to 35 percent of all conceptions). Day 60 – elective examination that has no specific reason, but has become more important since the advent of fetal sexing. If the mare aborts her pregnancy around Day 40-45 or after, it is unlikely she can get pregnant again the same breeding season anyway. Day 45 – elective examination that has no specific reason since endometrial cups should already be formed by this time. Day 26 to 30 – confirms heartbeat and fact that fetus is alive. Typical intervals for checking mares are: Day 14 to 16 – confirms initial pregnancy and looks for twins. Experienced equine veterinarians can feel a mechanical bulge in a mare’s uterus by Day 30 to 35 of gestation. In some regions, veterinarians could use a sterile speculum to see if the cervix was tightly closed (indicating pregnancy) or relaxing (indicating the beginning of another heat cycle). Your veterinarian can perform transrectal ultrasound as soon as Day 26 of gestation to visualize a heartbeat and confirm fetal viability.īefore ultrasound was so widely available, many people relied on the fact that most mares will come back into heat 17 to 20 days after breeding if they have not conceived. If the mare does recognize the presence of the embryo, then the embryo will attach itself to the wall of the uterus on or about Day 17. If the embryo does not touch all portions of the uterus by day 16 of gestation, the mare will reject the embryo, and begin showing signs of estrus to begin the next “heat” cycle. Once the embryo descends into the uterus, it has to traverse the entire uterus to be recognized by the mare. This is important to remember since you can manipulate the uterine environment up until this stage. The egg is fertilized in the fallopian tubes and does not enter the uterus until it about Day 6 of gestation. Stress, fever, uterine infections, hormone abnormalities and twins can all cause a mare to spontaneously abort. There are many causes of early embryonic loss.
Horse embryos are not more fragile than other species it’s primarily that horses in general have poor reproductive performance (ability to maintain a conceptus). Is it to breed performance, show or pleasure horses? To maximize your reproductive dollar you have to decide what the goal of your reproductive program is. Equine reproduction costs money: Feed, electricity, labor, water bills, barns, employees, stud fees, transportation and veterinary bills.
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