Estrus (Heat) in Cow
How to get Cow in heat naturally:
1.What is Estrus?
Estrus is characterized as the period of sexual receptivity for the female (Senger, 2003).
On the dairy estrus detection is the deliberate act to monitor and record the event of estrus and if artificial insemination (AI) is the method of reproduction, the breeding of the cow takes place at this time.
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| Estrus cycle in Cow |
2.Normal Estrous Cycle in Cattle
A heifer has her first estrus, or heat, at puberty. The age at puberty is influenced by genetics, nutrition, and body weight. Heifers fed an appropriate diet will generally reach puberty between 9 and 15 months of age. Dairy heifers tend to reach puberty earlier, at 9 to 12 months, whereas beef heifers tend to reach it a bit later, at 13 to 15 months. The age at puberty for some cattle breeds, such as Brahman, can be as late as 24 months.
After puberty, a heifer continues to have regular estrous cycles every 21 days (the normal range is every 18 to 24 days). The estrous cycle in cattle is complex and regulated by several hormones and organs.
After puberty, a heifer continues to have regular estrous cycles every 21 days (the normal range is every 18 to 24 days). The estrous cycle in cattle is complex and regulated by several hormones and organs.
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| Phases of the bovine estrous cycle. key: E2 = estrogen and P4 = progesterone. |
The follicular phase of the estrous cycle refers to the narrow period of time right before estrus (heat) and ovulation (release of the egg for possible fertilization). During this phase, there is rapid growth of a dominant ovarian follicle and increased estrogen production.
A follicle is a structure containing an egg, also called an ovum, and other cells that can produce estrogen. A heifer or cow will generally have two or three groups of ovarian follicles—called waves—develop during a single estrous cycle (the range is one to four waves). One follicle in each wave will become the dominant follicle. Early in the estrous cycle, when the progesterone level is high, the dominant follicle will not ovulate. Instead, it will regress and allow another wave of follicles to emerge. The last wave occurs later in the estrous cycle when the progesterone level is low. The follicle that emerges as dominant during this wave will not regress. Instead, it will grow larger and produce increasingly more estrogen.
Estrus (Heat) and Ovulation
The high estrogen level produced by the dominant ovarian follicle causes the heifer or cow to show signs of estrus. This means she’s sexually receptive—she’s said to be “in heat”—and will stand to be bred or mounted by other cows, commonly referred to as “standing heat.” The heifer or cow may show other signs of estrus, such as having a clear mucous vaginal discharge and an increased activity level. She may also vocalize more and try to mount other cows. Estrus is considered the beginning, or “Day 0,” of the estrous cycle.
Besides causing the heifer or cow to show signs of estrus, the high level of estrogen produced by the dominant ovarian follicle also triggers the hypothalamus—a section of the brain—to release a surge of gonadotropin releasing hormone (GnRH) right before ovulation. GnRH causes the pituitary gland in the brain to release two other hormones—follicle stimulating hormone (FSH) and luteinizing hormone (LH)—which travel in the blood to the ovary to control what happens to the follicles.
FSH is secreted during and shortly after estrus and causes a new wave of ovarian follicles to develop. A surge of LH causes the dominant ovarian follicle to rupture approximately 24 to 32 hours later, thus releasing the egg. This is ovulation and marks the transition from the follicular phase to the luteal phase.
The Luteal Phase: The Developing Corpus Luteum
During the luteal phase of the estrous cycle, the remnants of the newly ruptured ovarian follicle develop into the corpus luteum and begin to produce progesterone, a steroid hormone needed to support and maintain a potential pregnancy if the egg is fertilized. Over the first 10 days of the estrous cycle, the corpus luteum matures and increases in size. The corpus luteum reaches its maximum size and produces the most progesterone at mid-cycle (around Days 9 and 10). Under the influence of high progesterone, waves of follicles continue to emerge and regress without a dominant ovarian follicle rupturing. A dominant follicle won’t rupture again until the progesterone level falls during the next follicular phase.
No Pregnancy
If the egg isn’t fertilized or the early embryo fails to develop, the uterus releases the hormone prostaglandin F2-alpha around Days 16 to 20 of the estrous cycle. Prostaglandin F2-alpha causes the corpus luteum to regress. This is called luteolysis and leads to a drop in progesterone.
The low progesterone environment allows the dominant ovarian follicle to emerge from the last wave of follicles and mature instead of regress. The dominant follicle produces enough estrogen to cause estrus, thus starting the next estrous cycle.
Pregnancy
If the heifer or cow becomes pregnant, the embryo prevents the uterus from releasing prostaglandin F2-alpha and the corpus luteum continues to release progesterone. The high progesterone level stops the heifer or cow from cycling—she won’t go into heat or ovulate. In a normal, healthy pregnancy, the embryo develops into a fetus. Gestation (the period between when the animal becomes pregnant and when she calves) lasts about 283 days. It’s desirable for a heifer to have her first calf when she’s 2-years-old. For that to happen, the heifer must reach puberty and become pregnant by 14 to 15 months of age.
Cyclicity
When a heifer or cow has an estrous cycle that’s normal in length and she displays normal estrous behaviors during heat, she’s said to be "cycling." When a heifer or cow isn’t pregnant but she’s not ovulating or showing signs of heat, she’s not cycling. Instead, she's "anestrus," which is sometimes described as being “acyclic.” Right after a heifer or cow calves, it’s normal for her to be anestrus for a short period of time. Sometimes a medical problem, such as ovarian cysts or an infection of the reproductive tract, can cause a cow to stop cycling. Another reproductive challenge is silent heat—when a heifer or cow appears to be anestrus but, in fact, she is cycling normally and just not showing signs of heat.
3. Reliable methods of Estrus Detection
Efficient and accurate estrus detection is the most important factor limiting reproduction in most dairy animals/herds. Efficiency defines the proportion of dairy animals seen in estrus of all animals eligible for showing estrus. Accuracy gives the percentages that were correctly identified as being in estrus. In a well-managed herd, the maximal estrus detection rate was found to be 60% of ovulations when dairy animals were observed two or three times daily. With continuous observations, the detection rate may increase to 95% in the second and later postpartum ovulations.
Failure to observe animals in estrus delays first service, lengthens estrus intervals, and is one of the primary factors lengthening projected average minimum calving to conception interval by increasing the number of days open. It contributes more to lengthy calving intervals than conception failure. In addition, inaccurate estrus detection lowers conception rate. Many animals are inseminated when not in estrus.
Efficient reproductive management depends on the ability to detect estrus. There should be a systematic program for estrus detection. Criteria of such a program:
Employees should be trained in proper methods for estrus detection, semen handling and artificial insemination. If there is shortage of labour, investment in estrus detection aids should be considered.
These increase the efficiency of the estrus detection; although best method is visual examination but it is difficult in herd.
Marker Animals: These are usually males that have been altered so that cannot mate but usually have sexual desire. These may be:
Teaser Animal:
These are surgically altered male, usually sterile. The most common method is vasectomy, removing the section of vas deferens. This prevents the sperm passage but still allowing the transmission of sexually transmitted diseases.
Gomer Animals:There is surgically or non surgically alteration in direction of penis. When penis is erected, its direction is not straight. So when it mounts the cow, copulation does not occur. These bulls should not be large in size and weight.
Androgenized Cow or Heifer:
These cows are treated with male hormones.
Electronic Heat Detection Device:
They can measure the pressure applied to the female back, the activity level of female or the changes in hormone level.
Chin Ball Marker: It is placed under the chin of the bull. It causes the paint to rub on the back of the cow on which it is mounted.
Ka Mar Heat Detector: This device contains red dye and is glued on the tail. If the cow is mounted, the pressure on the device causes the dyes to mix, creating a visible colour change.
Electronic Pedometers: These are motion sensors attached on the neck or fore leg. This sensor indicates the increased activity level associated with estrus by measuring the changes in amount of walking.
Blood or Milk Progesterone Kit: It is used to measure the progesterone level. Normally it is less than 1 ng. During diestrus it is 8-11n g/ml.
Heat Expectancy Table or Record: At the beginning of breeding season it can be used to generate a list of animals that should be cycle during a given time. Both primary and secondary signs should be recorded. It is also useful when animal will return to the next estrus specially in animal with silent heat.
Computerized Estrus Detection Aid: Patches equipped with transmitters are glued to the tail head. When the mounting activity begins, the transmitter depresses and signals are sent to the receiver. Mounting data includes transmitter number, date, time and duration of mount. These are sent to the receiver and downloaded to computer.
We may also use sniffer dogs or video camera to detect animals in estrus.
Efficient reproductive management depends on the ability to detect estrus. There should be a systematic program for estrus detection. Criteria of such a program:
Frequency of observation (three times a day minimum)
Time allotted for observations (10 minutes per time for a herd of 50 animals)
Assignment of employees to estrus detection (no other duties at estrus detection times)
Employees should be trained in proper methods for estrus detection, semen handling and artificial insemination. If there is shortage of labour, investment in estrus detection aids should be considered.
4. Estrus Detection Aids
These increase the efficiency of the estrus detection; although best method is visual examination but it is difficult in herd.
Marker Animals: These are usually males that have been altered so that cannot mate but usually have sexual desire. These may be:
Teaser Animal:
These are surgically altered male, usually sterile. The most common method is vasectomy, removing the section of vas deferens. This prevents the sperm passage but still allowing the transmission of sexually transmitted diseases.
Gomer Animals:There is surgically or non surgically alteration in direction of penis. When penis is erected, its direction is not straight. So when it mounts the cow, copulation does not occur. These bulls should not be large in size and weight.
Androgenized Cow or Heifer:
These cows are treated with male hormones.
Electronic Heat Detection Device:
They can measure the pressure applied to the female back, the activity level of female or the changes in hormone level.
Chin Ball Marker: It is placed under the chin of the bull. It causes the paint to rub on the back of the cow on which it is mounted.
Ka Mar Heat Detector: This device contains red dye and is glued on the tail. If the cow is mounted, the pressure on the device causes the dyes to mix, creating a visible colour change.
Electronic Pedometers: These are motion sensors attached on the neck or fore leg. This sensor indicates the increased activity level associated with estrus by measuring the changes in amount of walking.
Blood or Milk Progesterone Kit: It is used to measure the progesterone level. Normally it is less than 1 ng. During diestrus it is 8-11n g/ml.
Heat Expectancy Table or Record: At the beginning of breeding season it can be used to generate a list of animals that should be cycle during a given time. Both primary and secondary signs should be recorded. It is also useful when animal will return to the next estrus specially in animal with silent heat.
Computerized Estrus Detection Aid: Patches equipped with transmitters are glued to the tail head. When the mounting activity begins, the transmitter depresses and signals are sent to the receiver. Mounting data includes transmitter number, date, time and duration of mount. These are sent to the receiver and downloaded to computer.
We may also use sniffer dogs or video camera to detect animals in estrus.
ENDNOTE
Senger PL. Pathways to pregnancy and parturition. 3rd ed.
Frequently Asked Questions
What is the heat cycle of a cow?
The estrous cycle of cattle is the period from one estrus (heat, phase of sexual receptivity) to the next estrus. For the cow and heifer, this period averages 21 days, with a typical range of 18 to 24 days in length.
What are the signs of estrus or in heat in the cow heifer?
Observable signs of heat include mounting or attempting to mount other cattle, standing to be mounted by other cattle, smelling other females, trailing other females, bellowing, depressed appetite, nervous and excitable behavior, mud on hindquarters and sides of cattle, roughed up tail hair and vulva swelling.
Do cows have periods?
After puberty, a heifer continues to have regular estrous cycles every 21 days (the normal range is every 18 to 24 days). The estrous cycle in cattle is complex and regulated by several hormones and organs.
What are some signs of estrus?
Behavior signs of estrus include constant vocalizations, loss of appe- tite, restlessness, and social behaviors such as rubbing up against herd-mates. Physical signs that are demonstrated during estrus include redness and swelling around the vulva, and a thin mucous discharge from the vulva.
Do cows bleed when in heat?
Some cows and most heifers have a bloody mucus discharge one to three days after estrus, but onset of this symptom, called metestrous bleeding, is quite variable. High estrogen levels during estrus cause blood to leak from vessels near the surface of the uterus.
How far away can a bull smell a cow in heat?
A bull may be able to smell an in-heat cow some distance away if a breeze brings odors his direction. Bulls can often identify a cow in pre-heat up to two days before she actually comes into heat. A bull may keep close track of her -- staying near and guarding her from other bulls -- until she does come into heat.
How do you know if a cow is in silent heat?
A cow with a silent heat doesn't display any of the obvious signs, like licking or sniffing other cows, mounting, standing to be mounted, or acting nervous and excitable. However, she can still become pregnant, and the bull will know about it, even if they're vasectomised.
Will a bull mate with the same cow twice?
Yes...the bull will breed the same cow over again during the same cycle. Trouble with some virgin bulls is that some fall in love with one cow and will breed her over and over and ignore the other gals waiting in line.
At what age does a cow come in heat?
Breeding should occur when the heifer cow reaches puberty. Puberty is a function of breed, age, and weight. Most heifers will reach puberty and be bred by 12 to 14 months of age and will be between 55% and 65% of their mature weight when they first begin to exhibit estrous cycles.
Do pregnant cows mount other cows?
Cows, even pregnant, will mount other cows that are on heat.