Estrus Detection in Dairy Cows

A cow that is bred at the wrong time is a cow that costs you another three weeks. Good heat detection starts with knowing what you are looking for and giving it enough time every day.

Key points

Standing to be mounted is the signal you can trust most.
The cycle averages about 21 days, so record every heat and count forward.
Watch at set times, long enough, every day including weekends.
Lameness, footing and heat stress hide heat, so fix those first.
Train everyone who watches cows, and keep records the same day.

What heat actually looks like

The one sign that matters most is standing to be mounted. A cow in true heat will stand still while another cow rides her. Everything else is a clue that heat is close, but standing is the signal you can trust.

Other signs show up before and around that point. Some cows are restless, bellow more than usual, sniff and lick other cows, or rest their chin on another cow's back. Many drop a little in milk and eat less for a day. You may see clear, stringy mucus from the vulva and a swollen, moist vulva.

Standing to be mounted: the main sign
Mounting other cows: a sign of heat nearby, not proof
Chin resting, sniffing, licking other cows
Restlessness, more walking, less eating
Clear mucus discharge
Rough or scuffed tailhead and hair loss on the rump from being ridden

Know your cycle

The estrous cycle averages about 21 days, so a cow that cycles normally should show heat roughly every three weeks until she is bred and settles. Write down the date of every heat you see. If a cow was seen in heat and you can count forward about three weeks, you know when to watch her closely again.

Heat is short and many cows show it mostly at night or in the quiet hours. That is why one quick look a day misses cows. Cows also show heat more when they are on good footing and have room to move, and less when floors are slick or crowded.

Build a routine for observation

Pick set times to watch for heat that do not compete with milking chores. Standing and watching for a stretch of time in a pen where cows are loose, such as after milking when cows return and are relaxed, gives you the best view. Check on weekends and holidays the same as any other day.

Give the job to someone who cares about it and train them. Show new employees what a standing cow looks like, what a cow merely mounting looks like, and why the difference matters.

Watch at consistent times each day
Watch long enough for cows to settle and interact
Keep the observer separate from other tasks while watching
Record every heat on the same day it is seen
Check cows coming due for rebreeding by their calendar

Records that make detection better

Heat detection gets easier when you can see who is due. Keep a list of cows that calved and passed your voluntary waiting period, cows seen in heat but not bred, cows bred and now due to return, and cows that should be checked for pregnancy.

Look back every month. Which cows were bred twice with no sign between? Which cows have gone a long time since calving with no heat recorded? Those names are where your attention belongs. Your herd management software, a wall chart or a notebook all work if they are used every day.

Things that hide or fake heat

Lameness, slippery concrete, heat stress, poor body condition and overcrowding all reduce the visible signs of heat. A sore-footed cow often will not stand for a rider even when she is ready. Hot weather pushes more heats into the cooler night hours.

False alarms happen too. A cow that mounts others may be near heat or simply dominant. Cows already pregnant are sometimes ridden. Before you breed, use the full picture of signs, the record of her last heat and the date she calved, and ask your vet how to confirm doubtful cows are not already pregnant.

What to do when a cow is borderline

Some cows show only a little. She sniffs, she is restless, she is a bit off feed, but nobody sees her stand. In that case look at her last heat date, her calving date and any notes from the day before. If the dates fit a normal cycle and she shows several signs, many herds go ahead and breed. If the signs are weak and the dates do not line up, wait and watch her again.

Check her last recorded heat and calving date
Count the signs, not just one
Write down what you saw and what you decided
Recheck her about three weeks later if bred

Common mistakes

The most common error is watching too briefly. The second is breeding on a single weak sign, such as one mount, without any other clue. A third is poor record keeping, so a cow seen in heat has no written date and nobody knows when to look for her again.

Another mistake is blaming the cow when the problem is the setup. If many cows go unseen, look first at footing, comfort, crowding, observer time and training before assuming a fertility problem.

Looking only once, in passing
Breeding on one mount without other signs
Not recording heats the same day
Ignoring footing and lameness
Leaving detection to whoever has a spare minute

When to get help: If many cows are not showing heat or return to service repeatedly, ask your veterinarian or reproduction specialist to review your records and a few cows. Your extension dairy specialist can help you set up a simple observation routine.

Sources and further reading

Organization homepages are linked so you can search them for current guidance on this topic.

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