Page 86 - December 2017

“You can use the mare’s history as a guideline as to how frequently she should be checked.”
Dr. Ahmed Tibary, Professor of Theriogenology, Department of Veterinary Clinical Sciences at Washington State University..
MoniToring
Pregnancy
in MareS
by Heather Smith Thomas
not every conception ends in a successful pregnancy. There are various reasons for pregnancy loss, and it pays to monitor brood-
mares to make sure they are actually still pregnant (especially in early pregnancy) and that everything is going smoothly.
“We can’t start evaluating pregnancy with ultrasound until about 12 to 14 days,” says Dr. Ahmed Tibary, Professor of Theriogenology, Department of Veterinary Clinical Sciences, Washington State University. “Doing a pregnancy diagno- sis is not just about finding the embryo/vesicle. We also need to pay attention to the health of that vesicle and whether it is of appropriate size for that day of preg- nancy,” he says.
Dr. Peter Sheerin,
owner of Nandi Veterinary
Associates in New Freedom,
Pennsylvania, says there are
typical times that mares are
examined for pregnancy.
“We usually look at them 14
to 16 days after they’ve ovu-
lated or 15 to 17 days after
they were bred to see if they
conceived. We may check
again a couple days later,
depending on the situation
and if there’s a concern about
twins. We want to find twins early,” he says.
Sometimes a pregnancy will be lost when there are twins and they “fix” on the same side. This increases the chances that both will be lost. “This is one reason why we check mares at 14 days,” says Tibary. “The embryo does not stop its migration until day 16. If there are twins, you still have a chance to separate the embryos, which allows one to develop normally.
“If the vesicle does not stop moving after day 16, this is an indication something is wrong. The embryo
has to fix at the base of the horn by day 16 or it will not survive. Another thing we look for is where the embryo stops. If it fixes in the body of the uterus instead of at the base of a horn, it will likely not be carried to term. It has to fix at the base of one of the horns.
“We also look for presence of edema,” Tibary explains. “This tells us there is something wrong with the hormonal environment. If I see a pregnancy on ultrasound, but the uterus on palpation does not feel toned (nice and tubular) there is something wrong with either the uterus or the hormonal environment— particularly the level of progesterone.”
The next time a mare would be examined might be somewhere between 25 and 30-days gestation to check for a heartbeat. “We like to start seeing a proper embryo by day 21 or 22, and by day 25 we need to
see a heartbeat,” Tibary says. “If we do a pregnancy diagnosis at 14 days and everything looks good, we want to see the mare again at day 25 or 28. Then we can evaluate the presence of fetal heartbeat, growth of the vesicle, etc. The reason we do this is because there are situations in which the vesicle will develop and be maintained for as long as 30 days without a proper embryo inside it. These are sometimes called ghost pregnancies. It’s just the outer membrane sitting there; the embryo inside it died earlier.”
Examinations after 28 days would depend on the client and the veterinarian’s preference. “When I prac- ticed in Lexington, we would check the mares at 28
to 30 days, and then again at 42 to 45 days, to make sure that the fetus is continuing to grow and doing the things that it should,” says Sheerin. “If for some reason the mare has lost the pregnancy by that point, you could get a culture on her to make sure that infection wasn’t the cause. You may be fortunate enough that she lost it before the endometrial cups formed (which usually happens around 36 days). If that’s the case, you may have a chance to breed her again during this breeding season.”
In that situation, the mare would be able to return to heat and be bred, whereas if she lost the pregnancy after the endometrial cups have formed and started producing the hormones that keep her from coming back into heat, you are probably out of luck. “The endometrial cups are outgrowths on the placenta that produce the important hormone ECG in the pregnant mare, which cause the production of accessory CL
Dr. Peter Sheerin, owner of Nandi Veterinary Associates in New Freedom, Pennsylvania.
Heather Smith Thomas
84 SPEEDHORSE, December 2017
equine health