New foals are showing up around barnyards making other horse owners think about getting their mare bred.
For those considering raising foals, it’s important to better understand the mare during both normal and abnormal breeding cycles.
Owners or handlers of breeding stallions are responsible to present the mare to the veterinarian, according to Dr. Michelle LeBlanc, renowned equine reproduction specialist.
“The first examination is usually on the first or second day of heat,” LeBlanc said. “That typically consists of a rectal palpation, and I routinely do an ultrasound scan, possibly a vaginal speculum exam and a culture.”
If there’s no discharge, and the vagina appears normal in the ultrasound scan, LeBlanc doesn’t always culture the mare.
“At that time, you measure the size of the follicles to determine when it’s best to breed the mare,” LeBlanc said. “If we’re talking about a breeding from April through June, mares are typically bred either the third or fourth day of heat.”
Either at that point in time, or not until the next day, the veterinarian will give the mare a hormone shot. “Actually I prefer giving human chorionic gonadotropin,” LeBlanc said. “This is a hormone produced by women during pregnancy. It will artificially induce a mare’s follicle to ovulate 36 to 48 hours later.”
Everything is timed so that the mare is bred prior to ovulation. Since the egg dies a few hours after ovulation, the goal is to have the semen in the uterus waiting for the egg.
“If the mare is normal, I will ultrasound her again before breeding,” LeBlanc said. “That’s to determine the size and texture of the follicle, and whether or not she’s ovulated. If she ovulated, we won’t breed her.
“At the time the mare is bred, if by artificial insemination, we determine if the cervix is opening properly,” LeBlanc explained.
An ultrasound will be performed on the mare again 24 hours post-breeding. “It’s very important to verify that the mare ovulated,” LeBlanc said. “If there’s free fluid in the uterus, it is inflamed and may be infected. You’ve got a big problem.”
An ultrasound is performed on the mare again 14 to 16 days post-ovulation to check for a pregnancy.
“With a mare you know is a problem, prior to breeding we would perform a complete reproductive exam,” LeBlanc verified. “That would be a rectal palpation, an ultrasound, speculum exam, a digital exam of the cervix, and a culture. There would also be a cytology performed to study the cells.”
A thorough physical exam would be done to determine the mare’s reproductive conformation. “Is the angle from the anus to the vulva horizontal? Is she pooling urine in the vagina?” the veterinarian would clarify.
Additionally, LeBlanc would check to see if there were any there feces in the vagina? “Mares with poor reproductive conformation are very prone to contaminating themselves,” she explained.
The most common problem LeBlanc finds that mares have during breeding is an inability to clear fluid from the uterus. This typically elates to poor reproductive conformation.
“Problem mares often can’t clear their uterus quickly,” Dr. LeBlanc detailed. “Four to six hours after breeding, we lavage meaning wash the uterus and give a shot of the hormone oxytocin.
“At 24 hours post-breeding, if the mare’s uterus still has fluid, defined as edema, I’ll lavage it again,” LeBlanc continued. “At this point, I might infuse antibiotics into the uterus.
“If we breed a mare two cycles and she doesn’t get pregnant I start all over again,” LeBlanc said. “That includes a complete reproductive exam and also most likely a uterine biopsy.”
Several mare reproduction terms are important to known by those planning to raise foals, the veterinarian insisted.
Reproductive Cycle: The hormonal cycle in which a mare prepares her uterus for conception and produces an egg ready for fertilization. It usually lasts 21 days: five to seven days in heat (estrus), under the influence of estrogen; 14 to 17 days out of heat, under the influence of progesterone.
Ovary: The female reproductive organ that produces eggs; a typical female has two.
Follicle: The structure of the ovary where an individual egg develops. In a typical reproductive cycle, only one follicle on one ovary matures to produce an egg.
Ovulate: When a follicle ruptures and releases a mature egg ready for fertilization; the rupture itself is an ovulation.
Estrogen: The major reproductive hormone released by growing follicles on the ovaries; causes a mare to show heat.
Progesterone: The major reproductive hormone produced by the corpus luteum, a structure that forms on the ovary where an ovulation occurred; it causes a mare to go out of heat.