Cow Heat Cycle: Signs of a Cow in Heat, How Long It Lasts and Breeding Timing

A cow’s heat cycle lasts about 21 days, measured from one standing heat to the next, and Mississippi State University Extension puts the normal range at 18 to 24 days for cows and heifers (MSU Extension, The Estrous Cycle of Cattle). The heat itself is short: standing heat averages about 18 hours but can run anywhere from 8 to 24 (University of Missouri Extension, G2021), and dairy extension sources report heats of only 6 to 9 hours (UGA Extension; University of Kentucky). Ovulation follows roughly 30 hours after standing heat begins, which is why the hour you first see her stand matters as much as the day.

So the practical job is simple to describe and hard to do: catch each heat, write it down, and use that date to time the breeding and to predict the next heat. Once she is bred, the free Creatures cattle gestation calculator turns the breeding date into a calving date, no account needed, and a breeding record on her Creatures profile keeps the heats, services and pregnancy checks together (see recording a breeding). This guide covers the cycle, the signs of a cow in heat, when to watch, which detection aids help, when to breed, and what it means when she comes back into heat or never shows at all.

How long is a cow’s heat cycle?

The estrous cycle of a cow or heifer averages 21 days, with a typical range of 18 to 24 days, according to MSU Extension. University of Missouri Extension describes the same rhythm as estrus recurring every 17 to 24 days, depending on the length of the individual cow’s cycle (MU Extension G2021). In practice that means if you saw a cow in standing heat on the 1st and she was not bred, or was bred and did not settle, you should be watching her closely again from about the 19th to the 25th.

Day 0 of the cycle is the heat itself. After she ovulates, the ovary forms a corpus luteum, which produces the progesterone that holds off the next heat and, if she conceived, maintains the pregnancy. If she did not conceive, the corpus luteum regresses late in the cycle and she comes back into heat. MSU describes heat recurring every 18 to 24 days in sexually mature, open cattle, so a healthy, mature cow keeps repeating the cycle until she settles. The cycle is the same across breeds, from the beef and dairy breeds on the Creatures cattle page to small homestead cows.

A few cattle are not cycling at all, and they matter as much as the ones that are:

• Heifers before puberty. MSU Extension says heifers reach puberty, their first heat, at about 11 months on average, depending on genetics and weight. To calve at two years old, a heifer has to reach puberty by 14 to 15 months and conceive (MSU Extension).
• Cows recovering after calving. The postpartum period typically lasts 40 days or more. MSU notes that a beef cow has roughly 82 days between calving and rebreeding if she is going to calve once a year, which is the 365 days of a year minus her 283-day pregnancy.
• Pregnant cows. Progesterone suppresses heat during pregnancy in the vast majority of cows (more on the exceptions below).

If you are buying a heifer or a small family cow, ask the seller for her recorded heat and breeding dates; our guide to how much a mini cow costs covers what else to check before you buy. If you are planning a breeding season backward from a calving date, the cow gestation chart walks through the 283-day count and the milestones in between.

How long does a cow stay in heat?

Shorter than most new owners expect. The figure depends on whose cows were measured:

• University of Missouri Extension gives an average standing heat of 18 hours, with a range of 8 to 24 hours from cow to cow (G2021).
• Mississippi State University Extension breaks a heat into three stages: coming into heat (about 8 hours), standing heat (about 18 hours) and going out of heat (14 hours or more) (MSU Extension, Estrus (Heat) Detection in Cattle).
• Dairy specialists report much shorter heats. University of Georgia Extension says cows are in heat 6 to 8 hours (UGA Bulletin 1212), and George Heersche of the University of Kentucky gives an average standing heat of 8 to 9 hours that is “considerably shorter in some situations” (UK, Timing of Insemination).

The honest answer is that a heat can be over in well under a day, and that a cow you check only once a day can stand, ovulate and go out of heat between your visits. The whole display is easier to catch if you know what each stage looks like.

Coming into heat. MSU lists a cow that stands and bellows, smells and headbutts other cows, and tries to ride them but will not stand to be ridden herself. Her vulva is red, moist and slightly swollen, with a clear mucus discharge. MU adds that restlessness, vocalizing and nervousness can start anywhere from 4 to 48 hours before standing heat.

Standing heat. She stands to be mounted, rides other cows, bellows often and is nervous and excitable.

Going out of heat. She may still try to ride others, but she walks away when they try to mount her. She may still sniff other cows and show clear mucus.

Signs of a cow in heat

The single reliable sign is standing heat: she stands still and lets another cow, or a bull, mount her. MSU calls this “the surest sign of heat” (MSU Extension), and MU calls receptivity to being mounted the primary sign of estrus (MU Extension). A cow that walks out from under a mounting herdmate is not in standing heat yet, or has already gone out of it.

Everything else is a secondary sign. Secondary signs tell you which cows to watch, not which to breed. The ones extension services list most often:

• Mounting or trying to mount other cattle (MSU notes the cows most likely to mount are those in heat, just out of it, or due in the next day)
• Following and sniffing other cows, and resting her chin on another cow’s back
• Bellowing, restlessness, and nervous or excitable behavior
• A swollen, reddened vulva and a clear, stringy mucus discharge, sometimes smeared on her tail or rump
• Roughed-up hair on the tailhead and mud on her hindquarters and flanks from being ridden
• A drop in appetite, and in dairy cows a dip in milk yield

That list draws on MSU Extension and UGA Extension. UGA adds a useful caution: pregnant cows, and cows in the early half of their cycle, do not make good heat detectors, so a group of mostly bred cows will ride less and expose fewer heats.

Bloody discharge a couple of days after heat

Many owners see a bloody or blood-tinged mucus discharge a day or two after a heat and worry that something is wrong, or hope it means she is pregnant. It means neither. The University of Florida College of Veterinary Medicine describes it as a normal discharge of blood-tinged mucus, typically seen about 48 hours after the start of heat in roughly 40 percent of cycling cows and 60 percent of cycling heifers, and notes there is no correlation with conception (UF Drost Project). It is useful as a record, though: if you missed the heat, the discharge tells you one happened about two days earlier, so you can expect the next one roughly 19 days later.

Any discharge that is thick, cloudy, pus-like or foul smelling, or bleeding that is heavy or does not stop, is a different matter. Call your veterinarian.

When to watch for heat, and for how long

Standing heat can happen at any hour, but it is most likely at night. MSU Extension reproduces Cornell University figures showing the share of cows first showing heat signs in each part of the day:

• Midnight to 6 a.m.: 43 percent
• 6 a.m. to noon: 22 percent
• Noon to 6 p.m.: 10 percent
• 6 p.m. to midnight: 25 percent

The same publication sets the minimum effort at two checks a day, early morning and late evening, each lasting at least 30 minutes, and reports that checking four times a day finds nearly 20 percent more cattle in heat than checking twice (MSU Extension). UGA’s dairy guidance says early morning, noon and late evening watches of 20 minutes each are needed to see more than 90 percent of heats (UGA). A quick glance from the truck while feeding does not count: MSU recommends watching away from the feed bunk so eating does not mask behavior.

Conditions change how much you will see:

• Weather. More cows show heat at night in hot weather and more during the day in cold weather. Hot weather, high milk production, crowding and stress can all reduce mounting.
• Footing. Cattle mount more on dirt than on concrete, and they need nonslip footing and room to move.
• Identification. You cannot record a heat on a cow you cannot name. Readable, unique ID on every animal is the first requirement in MSU’s list, which is a good reason to sort out your ear tag system before the breeding season.

Whatever schedule you choose, MSU’s instruction for the people doing it is the part most often skipped: record the cow’s ID, the time, and every sign you saw, and record every heat you detect even if you are not breeding her on that one. A logged heat is what lets you predict the next.

Heat detection aids

Detection aids catch the mounting you were not there to see. Extension specialists agree they supplement visual observation rather than replace it (MSU Extension). The main types:

• Tail paint or chalk. A stripe of livestock marking paint or chalk across the tailhead is rubbed off when she stands to be mounted. It is the cheapest aid, but MU notes the paint needs reapplying often and works better in dairies, where cows come in to be milked, than on pasture, where rubbing and rain remove it (MU Extension).
• Mount detector patches. Adhesive patches glued over the tailhead change color after mounting, either a pressure capsule that turns red or a scratch-off coating. MU says a scratch-off patch counts as activated when at least half of the coating is gone. Low branches, gates and other cattle can trigger false positives, and patches can fall off.
• Chin-ball markers on a detector animal. A marker worn under the chin of a surgically altered “gomer” bull, or an androgenized female, leaves ink on the back of any cow he mounts. Making a detector animal involves surgery or hormones, and MU says a veterinarian should make those decisions.
• Electronic systems. Tailhead transmitters that log every mount, activity monitors that flag restlessness, and milk or blood progesterone testing. MU notes these are costlier and mostly used in intensively managed dairy herds or research.

For a small herd bred to a bull, such as a few Belted Galloway cows run with a herd sire on pasture, you may not need any of this: the bull is the heat detector. Detection matters most when you breed by artificial insemination on observed heats. If you are weighing AI against keeping a bull, our guide to artificial insemination costs for cattle prices the detection aids, semen and technician time side by side.

When to breed a cow in heat

Timing comes down to three numbers. Ovulation happens about 30 hours after standing heat begins (MU Extension); Heersche gives the range as 24 to 32 hours with an average of 28. The released egg stays fertile for less than 12 hours, and sperm need about 6 hours in the cow before they can fertilize (UK). So the goal is to have capable sperm waiting when the egg arrives, which means inseminating partway through the heat, not the moment you first see her stand.

MU recommends insemination about 12 to 18 hours after the start of standing heat with conventional semen, which is what the long-standing AM/PM rule delivers:

• A cow first seen in standing heat in the morning is bred that evening.
• A cow first seen in standing heat in the evening is bred the next morning.

Two refinements from the same sources. With sexed semen, MU suggests a slightly later window, 18 to 24 hours after the start of standing heat, because sexed sperm survive for a shorter time. And Heersche reports that once-a-day insemination at a consistent time gave fertility similar to the AM/PM rule in a large study, so if twice-a-day breeding is not workable, a fixed daily time is a reasonable fallback. Your AI technician or veterinarian can tell you what works for the semen you bought.

Many herds skip heat detection entirely and use a synchronization program with fixed-time insemination. Those programs use reproductive hormones on a set schedule, and the drugs and timing are a decision to make with your veterinarian, so this guide does not cover them. With natural service, the bull does the timing for you; your job is to record when he went in and came out.

Whatever you use, write down the breeding date and the bull or semen. That date is where the calving count starts: the cattle gestation calculator adds the 283-day average and shows a calving planning window, and the calving guide covers what comes at the end of it. If you are buying straws, see how much a straw of bull semen costs.

After breeding: return to heat and pregnancy checks

If a bred cow does not settle, she comes back into heat about one cycle later, so the classic check is to watch her again 18 to 24 days after breeding. A cow that stands again in that window is usually open.

The reverse is not a guarantee. MU notes that a small percentage of pregnant cows continue to show heat signs, so a return to heat “cannot be considered a definitive sign of non-pregnant status,” and a cow that does not return is not proven pregnant either (MU Extension). A pregnancy check settles it. NDSU Extension says ultrasound and blood tests can diagnose pregnancy as soon as 28 days after the last possible breeding date, and rectal palpation typically needs around 40 or more days (NDSU Extension). Your veterinarian will choose the method. If you plan to breed a cow that shows heat while you believe she is pregnant, check with your veterinarian first.

How soon after calving does a cow come back into heat?

Usually not for several weeks. MSU puts the postpartum recovery period at typically 40 days or more, and UGA’s dairy guidance expects cows to be cycling every 21 days by about 50 days after calving. The first ovulation after calving, or after puberty, is often a silent heat: MSU explains that she ovulates but does not show heat or stand to be mounted (MSU Extension). So the first heat you actually see is often her second cycle. MU adds that AI timed correctly can sometimes result in pregnancy on a silent heat, which is one reason some herds use timed programs.

When a cow is not showing heat

A cow that has gone well past the expected window with no heat seen may simply have heats you are missing, especially at night or on concrete. Try more frequent checks or a detection aid before assuming anything else. Beyond that, the common reasons are that she is already pregnant, is too soon after calving, is a heifer not yet at puberty, or is in poor body condition; MSU notes that good nutrition and health management shorten the periods when cows do not cycle. Reproductive tract infections and other disorders also stop normal cycles.

Call your veterinarian if a cow or heifer of breeding age has not been seen in heat for longer than you would expect, if she cycles at irregular or very short intervals, if she seems to be in heat constantly, or if she has an abnormal discharge. A reproductive exam is the only way to know which of these problems you have, and treatment is the veterinarian’s call.

How to track heats and breedings on Creatures

Heat detection lives or dies on the record, which is why extension guides keep telling producers to write down every heat. Creatures is a free place to keep that record on each cow, alongside her other health, breeding and calving history. Saving records needs a free account; the gestation calculator works for anyone.

1. Add the cow. Create a profile for each cow or heifer with her ear tag or name, so every heat is logged against the right animal.
2. Log each heat. Open her profile, choose Add record, then Breeding & Reproduction, and pick the heat tracking category. Enter the date and, in the notes, the time you saw her stand and the signs you saw (standing, clear mucus, a rubbed patch, blood two days later). The walkthrough is in adding a record.
3. Set a reminder for the next heat. A heat record does not project the next one by itself, so add a Reminder about 18 days out for your watch window, or turn on Repeat every with an interval that matches your herd’s cycle while she is open. Reminders show in her care schedule and on your Today view; see reminders and upcoming care.
4. Record the breeding. When she is bred, add a Breeding & Reproduction record, turn on Track as breeding cycle, choose the service method (AI, natural service and others), and name the bull from his Creatures profile or as plain text. Use a single date for an insemination, or a service start and end date for the days a bull ran with her; Creatures widens the likely window for an exposure period. You get a projected calving date and window, plus milestones such as a pregnancy check from about day 28. See recording a breeding.
5. Watch the herd from one screen. The Breeding dashboard lists every active breeding in due-date order with Expecting, Due soon and Overdue counts. If a bull goes in with a whole group, you can record the breeding for the group in one save rather than cow by cow.
6. When she comes back into heat. If you record a new service for a cow that already has an active breeding, Creatures asks which breeding it belongs with and offers three choices: Replace it (she came back into heat, so the earlier breeding ends and the new one is tracked), Same heat (a second service in the same heat, added to the first breeding), or Keep both. It suggests one from the gap between the dates. If a pregnancy check comes back open instead, the breeding can be ended with End and remind me to rebreed, which adds a reminder around the date of her next expected heat. Tracking the rest of the pregnancy is covered in tracking pregnancy and progress.

Over a few seasons, that record answers the questions that matter at culling time: which cows cycle early after calving, which ones took two or three services, and which bull’s breedings settled. Our cattle record keeping guide covers what else is worth keeping from breeding to sale.

Cow heat cycle FAQ

How often does a cow go into heat?

About every 21 days, with a normal range of 18 to 24 days, until she is pregnant (MSU Extension). Individual cows vary, which is why recording each cow’s own heats beats relying on the average.

How long is a cow in heat?

Standing heat averages about 18 hours in University of Missouri figures, with a range of 8 to 24 hours. Dairy extension sources (Georgia and Kentucky) report shorter heats of 6 to 9 hours. Add several hours of lead-in and tail-off behavior on either side.

What is the surest sign a cow is in heat?

She stands still and lets another cow or a bull mount her. Mounting others, bellowing, clear mucus and a swollen vulva are secondary signs that tell you to watch her more closely.

When should I breed a cow after I see her in heat?

With AI and conventional semen, about 12 to 18 hours after standing heat starts: bred in the evening if first seen in the morning, and the next morning if first seen in the evening. Sexed semen is usually timed a little later. Ask your technician about the semen you are using.

Does a cow bleed when she is in heat?

Not during the heat itself. The University of Florida puts blood-tinged mucus about two days after the heat began at roughly 40 percent of cycling cows and 60 percent of cycling heifers. It is normal, it does not mean she is pregnant, and it does not mean she failed to conceive. Heavy bleeding or a foul discharge is a reason to call a veterinarian.

Can a pregnant cow show heat?

A small percentage can, according to MU Extension, so a heat after breeding is not proof she is open. Confirm with a pregnancy check before rebreeding.

How do horses compare?

Mares also run on about a 21-day cycle, but the Merck Veterinary Manual describes most mares as seasonal, cycling when days are long, with heat lasting 2 to 8 days rather than hours. The mare heat cycle guide covers the differences.

Do this next on Creatures

Whether you are logging your first heats on a family milk cow or planning an AI season for a beef herd, these are the useful next steps. Breed profiles, guides and tools for every kind of cattle are on the Creatures cattle page, including the Belted Galloway.