What is an estrous cycle in animals?
Estrous cycles start after sexual maturity in females and are interrupted by anestrous phases, otherwise known as "rest" phases, or by pregnancies. Typically, estrous cycles repeat until death. These cycles are widely variable in duration and frequency depending on the species.
What is estrus in mammals?
Estrus is commonly seen in the mammalian species, including primates. This phase is sometimes called estrum or oestrum . In some species, the labia are reddened. Ovulation may occur spontaneously in others. Especially among quadrupeds, a signal trait of estrus is the lordosis reflex, in which the animal spontaneously elevates her hindquarters.
What determines the timing of oestrus in animals?
Generally speaking, the timing of oestrus is coordinated with seasonal availability of food and other circumstances such as migration, predation etc., the goal being to maximize the offspring's chances of survival. Some species are able to modify their oestral timing in response to external conditions.
When does a female dog have her first estrus cycle?
Dogs will have their first estrus cycle when they reach puberty. Estrus is the stage of the reproductive cycle in which the dog can become pregnant; sometimes a dog that is in estrus is said to be "in heat" or "in season". On average, puberty or sexual maturity is reached at about 6 months of age,...
What is estrous cycle in animal?
The estrous cycle refers to the reproductive cycle in rodents. It is similar to the human reproductive cycle, commonly called the menstrual cycle (ovarian and uterine cycles). The estrous cycle has four phases, namely proestrus, estrus, metestrus and diestrus and lasts for 4 to 5 days [4] (Table 1).
What happens in estrus cycle?
Estrus is the period when high amount of estrogen is presents in the blood. The estrogen produces the behavioral signs of estrus, such as the mounting of other cows, the willingness to stand while mounted by other cow, and general increase of activity. Estrus is followed by a 3 to 4 day period referred to as metestrus.
What is an example of a estrus animal?
Cattle. Female cattle, also referred to as "heifers" in agriculture, will gradually enter standing estrus, or "standing heat," starting at puberty between 9 and 15 months of age. The cow estrous cycle typically lasts 21 days. Standing estrus is a visual cue which signifies sexual receptivity for mounting by male cattle ...
What is an estrus cycle with examples?
Estrous cycle definition tells us that Estrous cycles usually repeat themselves before a woman dies. Bloody vaginal discharge in some species is sometimes confused for menstruation. Some of the oestrous cycle examples may include rats, mice, horses, pigs that tend to have this form of the reproductive cycle.
What is estrus cycle in cow?
The estrous cycle of the cow is generally about 21 days long, but it can range from 17 to 24 days in duration. Each cycle consists of a long luteal phase (days 1-17) where the cycle is under the influence of progesterone and a shorter follicular phase (days 18-21) where the cycle is under the influence of estrogen.
How long is the estrus cycle?
Estrus is the stage when the dog can become pregnant. Although this can vary with each individual, on average a dog will be in heat for 1 ½ to 2 weeks but this can be shorter or longer.
What is the difference between estrus and estrous?
Estrus is commonly called “heat.” Estrous is an adjective used to describe things related to estrus, such as the behaviors associated with estrus (estrous behaviors) or the period from one estrus to the next (estrous cycle).
What is the difference between estrous cycle and menstrual cycle?
For example- cow, dog etc. Note: The oestrous cycle in cows is for 21 days whereas the menstrual cycle in humans is for 28 days. There are 4 phases in the estrus –proestrus, estrus, metestrus and anestrus. The oestrous cycle usually is followed till the death but the menstrual cycle ceases after 45 -50 years of age.
What are the 4 phases of the estrous cycle in dogs?
The canine estrous (reproductive) cycle is made up of 4 different stages. These are proestrus, estrus, diestrus, and anestrus. Each stage has differing signs related to behavior, physical or clinical changes, hormonal changes, physiologic changes, and cytologic (vaginal smear) changes.
How long is the estrous cycle in cattle?
The normal duration of an estrous cycle in cattle is 18–24 days. The cycle consists of two discrete phases: the luteal phase (14–18 days; metestrus and diestrus) and the follicular phase (4–6 days; proestrus and estrus). The luteal phase is the period following ovulation when the corpus luteum ...
What is the estrous cycle?
The estrous cycle represents the cyclical pattern of ovarian activity that facilitates female animals to go from a period of reproductive receptivity to nonreceptivity ultimately allowing the establishment of pregnancy following mating. The normal duration of an estrous cycle in cattle is 18–24 days. The cycle consists of two discrete phases: the luteal phase (14–18 days; metestrus and diestrus) and the follicular phase (4–6 days; proestrus and estrus). The luteal phase is the period following ovulation when the corpus luteum (CL) is formed, while the follicular phase is the period following the demise of the CL (luteolysis) until ovulation. During the follicular phase, final maturation and ovulation of the ovulatory follicle occurs which leads to the release of an oocyte (the female gamete) into the oviduct allowing the potential for fertilization.
What is the longest phase of the vaginal cytology?
The vaginal cytology during metestrus consists of many leukocytes along with nucleated cells and cornified cells. Diestrus is the longest phase, lasting roughly 57 h, and the vaginal smear consists primarily of leukocytes ( Fox and Laird, 1970; Maeda et al., 2000 ). Sign in to download full-size image.
How long does it take for a female rat to synchronize her estrous cycle?
A high percentage of female rats will synchronize their estrous cycle 3 days after being withdrawn from daily injections of progesterone ( Shirley, 1978 ). Stimuli associated with introduction of rats to a new environment caused the rats to begin new estrous cycles. Rats with 4- and 5-day cycles responded differently, but within both groups partial synchronization of estrous cycles occurred ( Shirley, 1978 ). Subcutaneous injection of LH-releasing hormone agonist was successful in synchronizing SD female rats to the proestrus or estrus phase 96 h postinoculation ( Borjeson et al., 2014 ).
What is the cytology of the estrus phase?
During the estrus phase, cytology consists initially of approximately 75% nucleated cells and 25% cornified cells, which then progress to a majority of swollen cornified cells without nuclei. In the later hours of estrus, the cornified cells appear degenerate and may appear to form an epithelial pavement.
What happens during the follicular phase?
During the follicular phase, final maturation and ovulation of the ovulatory follicle occurs which leads to the release of an oocyte (the female gamete) into the oviduct allowing the potential for fertilization. Commencement of regular estrous cycles in cattle occurs at the time of puberty.
How often does the estrous cycle occur?
The durations of the various stages of the estrous cycle vary with species and can, depending on the animal in question, either occur throughout the year, multiple times within an ovulatory season that is dependent on photoperiod (long-day or short-day polyestrous animals) or only once a year ( Senger, 2003 ).
What is the estrous cycle?
The estrous cycle (derived from Latin oestrus; "frenzy", originally from Greek οἶστρος, oîstros; "gadfly") is the set of recurring physiological changes that are induced by reproductive hormones in most mammalian therian females.
When do estrous cycles start?
Estrous cycles start after sexual maturity in females and are interrupted by anestrous phases, otherwise known as "rest" phases, or by pregnancies. Typically, estrous cycles repeat until death. These cycles are widely variable in duration and frequency depending on the species.
What is the difference between oestrous and menstrual cycles?
One difference is that animals that have oestrous cycles resorb the endometrium if conception does not occur during that cycle. Animals that have menstrual cycles shed the endometrium through menstruation instead. Another difference is sexual activity.
How long is the oestrous cycle of buffalo?
Buffalo have an oestrous cycle of about 22 to 24 days. Buffalo are known for difficult eostrus detection. This is one major reason for being less productive than cattle. During four phases of its oestrous cycle, mean weight of corpus luteum has been found to be 1.23±0.22g (metoestrus), 3.15±0.10g (early dioestrus), 2.25±0.32g (late dioestrus), and 1.89±0.31g (pro-oestrus/oestrus), respectively. The plasma progesterone concentration was 1.68±0.37, 4.29±0.22, 3.89±0.33, and 0.34±0.14 ng/ml while mean vascular density (mean number of vessels/10 microscopic fields at 400x) in corpus luteum was 6.33±0.99, 18.00±0.86, 11.50±0.76, and 2.83±0.60 during the metestrus, early diestrus, late diestrus and proestrus/estrus, respectively.
What is the spelling of "estrus"?
In British and most Commonwealth English, the spelling is oestrus or (rarely) œstrus. In all English spellings, the noun ends in -us and the adjective in -ous. Thus in North American English, a mammal may be described as "in estrus" when it is in that particular part of the estrous cycle .
How long does a cat's oestrous cycle last?
Even within species significant variability can be observed, thus cats may undergo an oestrous cycle of 3 to 7 weeks. Domestication can affect oestrous cycles due to changes in the environment. For most species, vaginal smear cytology may be used in order to identify oestrous cycle phases and durations.
How many times can a cat go into heat?
Some species, such as cats, cows and domestic pigs, are polyoestrous, meaning that they can go into heat several times per year. Seasonally polyoestrous animals or seasonal breeders have more than one oestrous cycle during a specific time of the year and can be divided into short-day and long-day breeders:
What is the term for the period of a female mammal?
Estrus, also spelled Oestrus, the period in the sexual cycle of female mammals, except the higher primates, during which they are in heat— i.e., ready to accept a male and to mate. One or more periods of estrus may occur during the breeding season of a species.
What happens to the endometrium before ovulation?
Prior to ovulation the endometrium (uterine lining) thickens, in preparation for holding the fertilized ova. As the proliferation of uterine tissue reaches its peak, receptivity is highest—this is the estrous period. Some animals ( e.g., dogs) are monestrous, having only one heat during a breeding season.
How do males know if a female is in heat?
Males can recognize a female in heat by smell; certain substances (pheromones) are secreted only at this portion of her cycle. The female’s genital area may be swollen during estrus, and she may show by a variety of behavioral signals that she is ready to mate.
Do dogs come into heat?
Some animals ( e.g., dogs) are monestrous, having only one heat during a breeding season. Others ( e.g., ground squirrels) are polyestrous: if not impregnated, they will come into heat repeatedly during the breeding season. Males can recognize a female in heat by smell; certain substances (pheromones) are secreted only at this portion of her cycle. ...
How long does an estrus last?
Although this can vary with each individual, on average a dog will be in heat for 1 ½ to 2 weeks but this can be shorter or longer.
How long does it take for a dog to cycle?
It can take up to two years for a female dog to develop regular cycles. There is no time of year that corresponds to a breeding season for (domesticated) dogs except for Basenjis and Tibetan Mastiffs which typically tend to cycle in the spring.
How often do dogs go into heat?
Most dogs come into heat twice per year, or about every six months, although the interval can vary between breeds and from dog to dog. Small breed dogs may cycle three times per year, while giant breed dogs may only cycle once every 12 months. When young dogs first begin to cycle, it is normal for their cycles to be somewhat irregular.
When do dogs reach puberty?
On average, puberty (or sexual maturity) is reached at about six months of age, but this can vary by breed. Smaller breeds tend to have their first estrous cycle at an earlier age, while large and giant breeds may not come into heat for the first time until they reach eighteen months to two years of age.
What is the term for when a dog is in heat?
Each cycle consists of several stages; the stage called estrus refers to when the female can become pregnant. Often a dog that is in the estrus stage is said to be in heat or in season.
How long does the estrous cycle last?
The estrous cycle has four phases, namely proestrus, estrus, metestrus and diestrus and lasts for 4 to 5 days [4] (Table (Table1).1).
What is the origin of the word "estrus"?
The word “estrus” was first used by Heape [13]. This is a Latin adaptation of the Greek word “oistros” which means “sexual season”, “gadfly”, “frenzy”, “sting” or “madness” [14]. Heape further named and defined the phases of the mammalian estrous cycle into proestrus, metestrus, diestrus and anestrus.
What are the three types of cells in the vagina?
The vaginal secretion is made up of three types of cells. They include leucocytes, cornified epithelial cells and nucleated epithelial cells. Estimation of the phase of estrous cycle is based on the proportion of these cells in the vaginal secretion [4] (Table (Table33and Fig. Fig.44). Table 3.
When does a female rat have her period?
In female rats, puberty is preceded by the pulsatile release of luteinizing hormone (LH) after the 4th postnatal week, approximately 30 days old [9]. This period is the anestrus and occurs about 8 to 9 days before the first proestrus [10]. The first proestrus, estrus, metestrus and diestrus then follow.
What are the phases of the menstrual cycle?
On the other hand, in humans, there are three phases of the menstrual cycle; the menstrual, proliferative (follicular), and secretory (luteal) phases. This cycle begins at puberty.
When does the reproductive period start in mice?
The reproductive period and estrous cycle of mice commences about the 26th day after birth with the opening of the vagina, which is about 10 days before vaginal cornification [7]. The apoptosis-mediated vaginal opening is an essential secondary character in mice, which is used as a predictor of puberty [8].
What animals are used in biomedical research?
Although, the choice of animal in biomedical research for a particular investigation may be controversial and highly opinionated, experimental animals commonly used include mice, rats, and rabbits. Small rodents like mice and rats are more preferred to larger animals like rabbits, dogs, cats, pigs and monkeys [2].
What is the estrous cycle?
Estrous cycle is the reproductive cycle of females of non-primate mammals. Therefore, estrous cycle occurs in females of non-primates such as cows, domestic pigs, sheep, goats, deer, elk, horses, hamsters, ferrets, canines, dioestrous, bears, foxes, and wolves, etc. The endometrium is reabsorbed by the walls of the uterus in these animals.
How long does the estrous cycle last?
Generally, the estrous cycle repeats after 21 days. Female animals are sexually active only during the estrus phase of the cycle. Estrous cycle is less complex than the menstrual cycle. It has four short phases: proestrus, estrus, metestrus and diestrus.
What is the difference between a menstrual cycle and an estrous cycle?
Another major difference between estrous and menstrual cycle is that during the estrous cycle, the endometrium is reabsorbed while during the menstrual cycle, the endometrium is shed via bleeding.
What are the two cycles of a mammal?
Estrous and menstrual cycles take place in mammals. Both cycles start after sexual maturity in females and continue till menopause. These cycles are driven by reproductive hormones in females. They prepare female mammals for holding a child during pregnancy.
Why do females have oestrous cycles?
Reproductive hormones induce these cycles in females. These cycles happen in order to prepare female mammals for holding a child during pregnancy. Oestrous cycle occurs in non-primates such as cows, sheep, horse, rabbit, and pig, etc. The menstrual cycle occurs in primates such as monkeys, apes and humans, etc.
Which cycle is reabsorbed in monkeys?
The menstrual cycle occurs in primates such as monkeys, apes and humans, etc. Endometrium is reabsorbed in the estrous cycle while it is shed in the menstrual cycle.
What is the period of menstruation?
Furthermore, the menstrual cycle starts after sexual maturity (at puberty) and continues till menopause. There are three major phases of the menstrual cycle. They are menstrual, proliferative (follicular), and secretory (luteal) phases. Ovulation occurs in the ovulatory phase.
Overview
Specific species
The female cat in heat has an estrus of 14 to 21 days and is generally characterized as an induced ovulator, since coitus induces ovulation. However, various incidents of spontaneous ovulation have been documented in the domestic cat and various non-domestic species. Without ovulation, she may enter interestrus, which is the combined stages of diestrus and anestrus, before reentering estrus. With the induction of ovulation, the female becomes pregnant or undergoes a …
Differences from the menstrual cycle
Mammals share the same reproductive system, including the regulatory hypothalamic system that produces gonadotropin-releasing hormone in pulses, the pituitary gland that secretes follicle-stimulating hormone and luteinizing hormone, and the ovary itself that releases sex hormones, including estrogens and progesterone.
However, species vary significantly in the detailed functioning. One difference is that animals th…
Etymology and nomenclature
Estrus is derived via Latin oestrus ('frenzy', 'gadfly'), from Greek οἶστρος oîstros (literally 'gadfly', more figuratively 'frenzy', 'madness', among other meanings like 'breeze'). Specifically, this refers to the gadfly in Ancient Greek mythology that Hera sent to torment Io, who had been won in her heifer form by Zeus. Euripides used oestrus to indicate 'frenzy', and to describe madness. Homer used the word to describe panic. Plato also used it to refer to an irrational drive and to describe the soul "dri…
Four phases
A four-phase terminology is used in reference to animals with estrous cycles.
One or several follicles of the ovary start to grow. Their number is species-specific. Typically this phase can last as little as one day or as long as three weeks, depending on the species. Under the influence of estrogen, the lining of the uterus (endometrium) starts to develop. Some animals may experience vaginal secretions that could be bloody. The female is not yet sexually receptive…
Cycle variability
Estrous cycle variability differs among species, but cycles are typically more frequent in smaller animals. Even within species significant variability can be observed, thus cats may undergo an estrous cycle of 3 to 7 weeks. Domestication can affect estrous cycles due to changes in the environment. For most species, vaginal smear cytology may be used in order to identify estrous cycle phases and durations.
Frequency
Some species, such as cats, cows and domestic pigs, are polyestrous, meaning that they can go into heat several times per year. Seasonally polyestrous animals or seasonal breeders have more than one estrous cycle during a specific time of the year and can be divided into short-day and long-day breeders:
• Short-day breeders, such as sheep, goats, deer and elk are sexually active in fall or winter.
See also
• Mating system
• Musth
• Neutering
• Progesterone-releasing intravaginal device
• Reproductive cycle