This article, will make clear that the mare and her management are also factors of great importance for having the best possible chance of pregnancy. It is always advisable to inoculate the mare. for influenza and tetanus, but even more important to do so if she will be taken to a stud station since this is a location where horses from various locations are brought together and the risk of a catching a cold is somewhat greater here.

First of all, the mare owners must make sure that they are offering a healthy mare for covering. This means that not only the mare's general condition and health status must be good, but also that her sexual organs must be in good condition to obtain the greatest chances of pregnancy following insemination/natural covering. Mares that have never conceived should be carefully examined before being offered for stud service. Did you know, by the way, that if you offer a mare with a sexually transmitted disease for natural cover and the stallion then infects other mares that you will be liable? When dealing with mares that have just foaled, it is important to know how foaling progressed and the period of time between the birth of the foal and the expulsion of the placenta. For about 30% of Friesian mares, this time period is too long. For this reason, as soon as 2 hours after foaling, it is advisable to ask the veterinary to inject the mare with oxytocin (an agent that will make the uterus contract). If, after 6 hours, the placenta must be removed by hand, it will be necessary to flush the uterus for several days and to administer antibiotics and oxytocin so that the uterus can recover quickly. If it took the mare longer than 6 hours to expel the placenta, or if she is older than 12 years, it is not advisable to have her covered during her foal heat since the uterus will not have had sufficient time to recover.

Determining the best time to cover
Determining the proper time for insemination/covering is best done by teasing and follicle monitoring. A mare in heat will stand by the stallion. If he noses her flank, she will turn her head toward him, the lips of her vulva will wink, and she will release large quantities of usually cloudy urine. It can also be the case that a mare that is actually in heat will exhibit no clear signs of this (e.g. if she is afraid, as some young mares are, or if she wants to protect her foal).
The veterinary conducting the follicle monitoring will feel to see if there is a large ovarian follicle in the ovary, if this feels soft, and if the uterus and Cervix are slack. If so, this is the best possible time for insemination. It is also possible to use ultrasound to see exactly how large the follicle is, if there is more than a large follicle present, and if there is no liquid in the uterus. If the mare is then inseminated (with at least 300 million TNB), a check will be made after 24 hours (when frozen semen has been used because this has a shorter life span) or after 48 hours (when fresh semen has been used) to see if ovulation has occurred. If not, the mare must be inseminated again. It is advisable, however, not to have the mare inseminated too often during a single cycle because not only can this be a hardship on the stallion but the mare's uterus will have to process all of this foreign material (semen). The uterus reacts to this by producing liquid and the mare's body increases its production of white blood cells to get rid of this foreign material. We have often heard the mark that mares are allergic to semen extender, but research has shown that the mare's uterus reacts just as strongly to undiluted semen as to diluted semen. When checking for ovulation, we can also find out if more than one ovarian follicle has been released. If so, and if the mare becomes pregnant, there is the chance of twins.

Testing for pregnancy
If the mare has released a single ovarian follicle, we can check her for pregnancy in about 18 days to see if she is pregnant. If not, she may again be starting another cycle of heat. If she has produced two ovarian follicles, it is then advisable to perform an ultrasound scan 16 days after ovulation to see if she is pregnant because by that time, the embryos will not yet be implanted in the uterus and it will be easier to remove one. A disadvantage, however, is that the mare (usually a somewhat older one) can also have cysts in her uterus that can easily be confused so early in pregnancy with an embryonic vesicle. If the embryos have already become implanted and are close to one another, it will also be difficult to remove one without harming the mare. A possible solution, in case of discovering twins during a somewhat later stage of pregnancy when they are positioned close together, is to puncture one of the membranes surrounding one of the embryos and drain it that will thus cause that embryo to die. If the mare has conceived and everything is running normally, we will be able to see a beating heart in a second pregnancy check when an ultrasound is performed between day 25 and 30. The timing for these checks is important because this early period is often accompanied by the early death of an embryo (premature embryonic death). Around week 6, the mare can be checked again since after 35 days, pregnancy is maintained by means of another hormonal route. This can sometimes lead to problems with the result being premature embryonic death. Around the third or fourth month, another check can be performed to see if the mare is still pregnant. This way, feeding and working can be taken into consideration with the pregnancy. After all, it sometimes happens that the mare has just conceived and is then taken away by the trainer for training and readying for the mare inspections. This puts additional stress on the mare that can lead to premature embryonic death. In general, however, there are no problems associated with working a pregnant mare.