Content
- When does the mares' heat period begin?
- Stages of the mare's estrous cycle
- Follicular phase of estrus in mares (7 to 9 days)
- Luteal phase (14 to 15 days)
- Symptoms of a mare in heat
- Does the horse come into heat?
- What is the colt heat?
The mares come into heat stimulated by the increasing photoperiod during the long days of the year, that is, when there is more sunlight and heat. If during these months the mare does not become pregnant, the cycles will be repeated every 21 days, on average, until the days become shorter again and the mare enters the resting phase of the heat cycle (seasonal anestrus). Her heat consists of an estrous phase characterized by behavioral changes and changes in her reproductive organs to accept the male, and a luteal phase in which she is no longer receptive and prepares for pregnancy and, if this is not the case, she repeats the cycle.
Do you want to know more about the mare in heat - symptoms and phases? Keep reading this PeritoAnimal article, where you'll find the information you're looking for to solve your doubts.
When does the mares' heat period begin?
Estrus begins when mares reach sexual maturity, which usually occurs when they are between 12 and 24 months deity. At this point, the mare's reproductive system begins to interact with other parts of the body, hormones begin to secrete and act and the first ovulation occurs, with its associated physical and behavioral changes being covered by the male at the right time to become pregnant. Although the mare less than two years old is already in heat, they will continue to grow until 4years old of age, which is when they will reach their maximum size.
The mare is a seasonal polyestric animal with long days, which means that its heat occurs when the daily light hours increase, ie, in spring and summer. During this period the mare goes into heat several times - which is repeated every 21 days, on average. Her ovaries are kept at rest during the other months of the year, entering the so-called anestrus, because when there are fewer hours of light, more melatonin is released by the pineal gland, a hormone that inhibits the hypothalamic-pituitary hormonal axis in the mare, which is what it stimulates the ovaries to produce the hormonal changes responsible for ovulation.
Certain conditions cause mares do not come in heat or are very irregular during the breeding season:
- Malnutrition or extreme thinness
- Advanced age
- Increased cortisol due to steroid therapy
- Cushing's disease (hyperadrenocorticism), which is the stress hormone and suppresses the mare's hormonal axis
This other article by PeritoAnimal with suggested names for horses and mares might interest you.
Stages of the mare's estrous cycle
The recurrent phases and events that are caused by the mare's reproductive hormones are called estrous cycle. The mare takes between 18 and 24 days to go through all phases, that is, in about 21 days, on average, the cycle will start again if she is in her breeding season. This cycle is divided into two phases: follicular phase and luteal phase, which have two stages each:
Follicular phase of estrus in mares (7 to 9 days)
During this phase, the blood vascularity of the mare's genital system increases, its walls have clear, shiny mucus, and the cervix relaxes and opens, especially around ovulation because the estrogens produced in this phase are increasing. At the same time, the vagina dilates, lubricates and becomes edematous, with the water becoming receptive to the male. This is divided into two periods:
proestrus: Lasts about 2 days, follicular growth stimulated by follicle stimulating hormone (FSH) occurs and estrogens begin to increase.
estrus: lasts between 5 and 7 days, also known as the estrus phase, ovulation or shedding of the preovulatory follicle, which should measure between 30 and 50 mm, depending on the height of the mare. Occurs 48 hours before the end of this step. In 5-10% of cases there is a double ovulation when two follicles develop, reaching up to 25% in the case of purebred mares, however, double pregnancy in mares is a danger.
Luteal phase (14 to 15 days)
After ovulation, estrogen decreases and progesterone increases in the corpus luteum (structure formed in the ovary from the follicle granulosa cells, hence the name of the phase), which lasts a maximum of 7 days after ovulation and leads to closure of the cervix , becoming pale and mucus free and the vagina drying and becoming paler. This is because this phase prepares the uterus to support the pregnancy, but if this has not happened, the mare will repeat the cycle at the end of it. In turn, this phase is divided into two:
- metaestrus: stage that lasts 2 to 3 days, where the corpus luteum is formed and the progesterone increases.
- Diestrus: lasts about 12 days, progesterone is still produced and at the same time the dominant follicle is developing so that it can ovulate in the next heat. At the end of this stage, the corpus luteum produces prostaglandins, which are responsible for breaking it down and the mare returns to heat in two or three days.
Symptoms of a mare in heat
There are a number of signs that indicate a mare in heat being, therefore, receptive to mating with the male. In addition to being more agitated, the mare in heat has these symptoms:
- Keep tilting your pelvis down.
- It lifts and deflects its tail to expose its vulva.
- It expels mucus and urine in small amounts to attract the male.
- Redness of the vagina.
- It exposes the clitoris by the repeated movement of the vulvar lips.
- She is receptive and affectionate, remaining still with her ears open and waiting for the male to approach her.
Each mare is unique, there are some that show very obvious signs and others that are very subtle, so sometimes horses are used to confirm whether the mare is in heat or not.
If the mares are not in heat and a male approaches them, they stay away, do not let them near, bend their tail to hide their genitals, put their ears back and they may even bite or kick.
Does the horse come into heat?
Male horses do not go into heat, as they do not go through the stages of the heat cycle like females, but from sexual maturity they always become fertile. However, in the females' heat season, they also become make more active stimulated by the mares.
This detection is done through pheromones that the mare in heat releases with the urine, which is thicker and opaque than normal, through the Flemen reaction. This reaction consists in the retraction of the upper lip when they smell urine, in order to detect the pheromones through the vomeronasal organ (an auxiliary smell organ in some animals, located in the vomer bone, which is found between the nose and mouth, which allows accurate detection of these compounds), along with petting, whinnying, and approaching the mare.
In this other article you will find out what are the most common diseases in horses.
What is the colt heat?
O heat of the foal is what is called the heat that appears between 5 and 12 days after delivery. It is a very early heat that occurs when the mare has postpartum physiological endometritis and her defenses are suffering from this process. Therefore, care must be taken not to leave the mare near a male in these situations, especially mares that come into heat before the 10-11 day postpartum, as her endometrium is still regenerating and if a male to cover, this will aggravate the mare's endometritis, which will decrease fertility.
If by chance she becomes pregnant, there may be a risk for her and the foal, with miscarriages, dystocic births, stillbirths or retained placenta, being more frequent in mares over 12 years of age or in those who had problems in the previous pregnancy.
Now that you know all about the mare in heat and the mare's estrous cycle, you might be interested in knowing what types of halters for a horse are.
If you want to read more articles similar to Mare in heat - Symptoms and phases, we recommend that you enter our Curiosities section of the animal world.