Another reason for exams, twins...
Another reason for exams, twins...
EARLY PREGNANCY EXAMS
We are able to perform an examination for pregnancy of the mare by using two methods. For an early examination, we use ultrasound. If time is not important and if the owner’s curiosity and anxiety tolerance is high, we can examine the mares by rectal examination. There are advantages to both. The ideal approach to managing the pregnancy is a combination of the two.
By using ultrasound, we can examine the mare anytime past the14th day after breeding. Of course days 14 to 20 are before the next heat. This is a very important reason for using the ultrasound for pregnancy examination. If we find the mare is not pregnant she can be returned to the stallion.
Other advantages of using the ultrasound is in diagnosing the presence of twins, and evaluating the health of the embryo. Twin pregnancies in the mare are very undesirable. If they become established, they are very likely to abort before seven to eight months of pregnancy. The babies will crowd each other until the uterine connection of one is disrupted. That one will die and decompose. The process of decomposing will then kill the dominant one. With both fetuses dead, the uterus signals the mare to deliver them. The dominant fetus is usually found with fetal tissues, as the mare sadly will stay with it for some time. The decomposed one may not be noticed, as there is little left.
One client brought us parts she found after her mare delivered a healthy foal. Once the delivery was complete, a somewhat round structure rolled out. It was the head of a fetus. There were probably other body parts that went unnoticed. Somehow, the lesser fetus decomposed without destroying the dominant one. This is probably very rare.
The presence of twins is pretty common. Relevant literature claims that as many as 25% of heats result in twin ovulations. If twins are diagnosed before they implant, and if they are developing separately, one can be maneuvered up the horn and destroyed. If the twins are located next to each other, it may be impossible to separate one. Then we must make the decision to terminate the pregnancy and start over (easier to recommend early in the breeding season), or allow the twins to develop. Frequently late in the season, we will leave the twins alone. They are so close together, one will establish dominance and destroy the other within a couple of weeks. We monitor these with the ultrasound until there is just one remaining twin.
As important as diagnosing the twins is diagnosing the retarded embryo. When we examine a mare at fourteen or more days and find a small embryo only a tenth the size we expect to see, we classify this as a retarded or slow growing embryo. The egg was fertilized and the resulting embryo dropped into the uterus at about five days of age. It must then travel from that end of the horn all the way over to the tip of the other horn and back to the body before the next follicle starts developing. This rapid and extensive travel is necessary to notify mother of its presence.
Some embryos just do not make the journey. They may also create a problem. If they have already sent a message to mother, and then the embryo dies, its presence may be enough to prevent the mare from cycling on schedule. She may come into heat once she decides the embryo is not alive, but this would be off-cycle and could be easily missed by the breeder. We will occasionally see these dead small embryos still present during the next pregnancy, and sitting contentedly along side the healthy embryo.
While all the above reasons for diagnosing pregnancies by ultrasound are good ones, there are some fun reasons as well. It is a pleasure to watch the heart beat of a fetus forty days or older. It is also possible to diagnose the sex of the baby between fifty and sixty days of age. They will be very active during that time, kicking and moving about. Watching this fully formed horse so active at less then a sixth of the way through pregnancy helps us realize how incredibly quickly they develop, and what a miracle it is.
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