When we refer to equine reproduction we must keep in mind that it involves both the Male and the Female, two living beings that procreate with the conception of their two gametes, having as a product another living being that will have the genetic load of both. parts.
In order to achieve this goal, many physiological processes need to be carried out in the animals involved. Certainly nature is perfect, but in some cases that physiology, which is a normal process that takes place in organisms, can be affected by pathological processes or external events that become obstacles to achieving that final goal, which is the conception.
Over the years, there have been many investigations that have been carried out on the negative factors that can affect a female or male in order to obtain the desired results, and at the same time studies that can solve these reproductive problems. It is also true that studies have been done to optimize the procedures, in order to have better use of individuals.
The world of horses is very large and selective, we always look for the best of the best, regardless of the breed or sporting discipline that is practiced with them, since there is always a constant genetic advancement of the specimens to be used, since If you want to succeed in sports practiced with horses, you need to reproduce the best animals of the moment to constantly develop and genetically improve them.
Due to this need for progress, we have sought to optimize the reproductive processes, that is, to obtain a calf it must be done in the most efficient way possible and thus be able to conserve these animals over time to be able to get the most out of it.
Equine reproduction is not immune to the advances that have been made in technology, since there are many tools that biotechnology has provided for its progress. It is good to note that not all breeds of horses such advancement is allowed, and the best example of this is in the Purebred Racing breed, which for years has basically maintained the same work scheme. For example, artificial insemination, which is a very common biotechnology today, is not allowed in this breed, since direct mating must be carried out, that is, a breeding male mounts the mare in a natural way.
But it is true that we can carry out detailed ultrasound monitoring of the mare to be served, to know the optimal moment for said act, and thus be able to expect the best results.
In underdeveloped countries and in non-professional horse breeding, it is difficult to find this breeding method, of keeping track of the reproduction of horses. This is where, in my opinion, we can find great challenges, since the fewer tools available to work with, the greater the creativity must be to be able to put some of them into practice and be able to meet the goals we set for ourselves.
In order to carry out studies that allow us to recognize the reproductive behavior of mares in their natural environment, we must know that mares are considered seasonal polyestrians with long days and their sexual behavior is regulated by the photoperiod.
The aforementioned refers to the fact that females of this equine species can have multiple estrous cycles throughout the year, these being regulated by the photoperiod, that is, the amount of sunlight that exists in a day.
Now everything can vary depending on the handling that these animals have. For example, animals that are in a traditional or natural system will behave in this way, but if we have animals under a stable system, which most of the time are locked in facilities suitable for them, the reproductive behavior will be different. , since artificial or unnatural management will be involved.
The estrous cycle of mares will always be accompanied by behavior that is divided into acceptance of the male of the same species (estrus) or rejection of him (diestro), according to Gary et al., 2007; Youngquist and Threlfall, 2007, “estrous behavior results in gradual changes over days where the mare can show sexual receptivity toward the male.”
It is important to note that this sexual behavior is not fulfilled in one hundred percent of the cases, since on some occasions we find individuals who in their physiological moment of acceptance of the male do not demonstrate it in their behaviors.
That is why the minimum necessary, among other things, for the establishment where the animals involved want to reproduce is to detect heat in the mare. If we run into problems at this stage, we will not be able to know or estimate the optimal service time. Indeed, we can evaluate the reproductive tract through ultrasonography and know the physiological state of the mare, but it is essential to observe the external characteristics so as not to make mistakes, and also so that inexperienced people can detect the moment.
According to Brinsko et al., typical expressions of estrus in a mare are observed through the presence of the breeding male, and are raising the tail, raising the pelvis along with urination position, urinating, and everting the clitoris.
Now, for mares that do not present the type of behavior mentioned in front of the male, it is called silent heat that may be due to social factors, some of which may be due to the absence of a reproductive male or due to the dominance of the mare. in the group.
It is important to highlight that animals that are characterized by silent heat present normal ovarian activity, that is, their physiological process of the reproductive tract functions adequately.
Silent heat can occur in the mare’s first heat after foaling, called “foal heat,” or any other heat. According to Parker, 2013, a common cause of postpartum silent heat in mares is their dominant maternal instinct by not showing it.
As Najjar et al 2019 comments, “some mares ovulate, without showing any external signs of heat, however, ultrasonographic examination reveals follicular activity close to ovulation. During the postpartum period, 20% ovulated silently, while the other 80% showed signs of heat. From a study of 59 Arabian mares.
Within my experience as a veterinarian I had the opportunity to monitor for three months (September-November 2018) the behavior of 24 mares of different breeds, such as quarter horse, racing thoroughbred and Colombian Creole. “Silent heat” was witnessed in 6 mares, this being 25% of the batch, while the other 75% expressed their heat. Of these six animals with an absence of signs of acceptance of the male, there were two mares of the Colombian breed, three racing thoroughbreds and a quarter horse.
In conclusion, it is very important to take into account the criteria to know when an animal is in heat. If at the time of the ultrasound examination we observe that the mare is in estrus but does not express it, we must carry out persevering work with the help of the male so that she expresses it and can be served without any risk to the staff and the horse. breeder, since if the mare does not show signs of heat, it is a sign of rejection of the male.
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