A transrectal ultrasound can be performed by your veterinarian as early as Day 26 of pregnancy to visualize a heartbeat and confirm embryonic viability. Prior to the widespread availability of ultrasonography, many people relied on the notion that most mares will go into heat 17 to 20 days after breeding if they have not conceived. This idea arose because most horses breed once a year and require time to recover between heats. Therefore, they were believed to need to come in contact with the stallion again around this time in order to conceive.
Today, most reproductive specialists agree that a viable fetus is able to survive outside of its mother for several weeks following conception. As such, there is no reason why a pregnant horse could not be scanned earlier than the typical waiting period recommended by some veterinarians.
An ultrasound examination is useful in determining the location and severity of any abnormalities within the uterus. This information can help guide treatment decisions during pregnancy, even if it is intended to be a single embryo transfer program. In addition, an ultrasound can reveal evidence of fetal death, which may explain why a mare appears to be carrying multiple embryos yet fails to become pregnant. Finally, an ultrasound can identify viable fetuses at risk of dying if left alone for several hours after being removed from their mothers' bodies at slaughterhouses or other locations where they are no longer being cared for by their mothers.
It is important to perform ultrasound examinations under proper conditions.
Tips Keep your veterinarian's contact information on hand at all times in case of an emergency. Mares generally remain pregnant for 320 to 360 days. If your mare is set to give birth in late winter or early spring, her pregnancy will last 5–10 days longer. If your mare was bred during the summer, her baby will arrive around July 4th.
A mare's labor can start anytime between 45 and 150 hours after she foals. A newborn equine usually weighs about 100 pounds and is about 1 foot tall. Her legs may be slightly bent under her body or straight out like a human infant's. She'll also have a mouth full of coltsions (baby teeth) when she first opens her mouth. These drop off over time unless she eats grass or other vegetation containing calcium that builds her bones instead.
The gestation period for a horse is about 11 months plus some days. This means that a mare's baby will come out around January 21st of the next year. However, this date can vary from as little as 10 months to as much as 12 months because many factors affect how long it takes for a mare to give birth including her age, health, and diet. For example, a young mare who is very hungry may give birth earlier than expected while an older mare who is not has enough energy may go into labor later in the year.
Because it is fairly uncommon for a mare to lose a pregnancy, it is advised that an ultrasound, blood, or urine test be performed again after around three months. Checking how a mare tosses her head, the expression in her eyes, or how a needle moves when held over her tummy are not reliable ways to determine if she is in foal. Should you discover she is in foal, call your veterinarian right away so he can take care of the newborn.
Most pregnancies will be lost before the equine equivalent of human miscarriage, which is about 12 weeks into gestation. A mare may appear to be carrying a foal and enter labor, only to collapse a few hours later without delivering the fetus. This may be due to losing the pregnancy before the equine equivalent of human pregnancy, which is around week 12. She may also have lost the pregnancy early through natural processes like miscariage.
Miscariage occurs when a mare loses her embryo or fetus before the equine equivalent of human pregnancy, usually because her body isn't compatible with the conceptus (fetus or embryo). This can happen at any time during her cycle, but most miscarriages occur between days 5 and 20 of her cycle. Miscarriage is common among mares and horses of all ages, but it's particularly frequent among young animals and those who are already pregnant. In fact, according to the American Veterinary Medical Association, up to 25% of all equine pregnancies end in miscarriage.