How long does pregnancy last in a cow?
In cattle, gestation lasts on average 280–285 days (about 9 months). It can vary by a few days with breed and with the individual. Recording the insemination date is the most reliable way of knowing the expected calving date.
On the farm this length mostly moves between 275–290 days. Cows carrying a bull calf calve slightly later on average, and those carrying twins markedly earlier. So think of the expected calving date not as a single day but as a window of a week. The practical rule is this: add 9 months to the insemination date, then add about a week. For a cow inseminated on 15 March, calving is expected around 22 December.
Whether that date is right depends on the insemination day in the book being right. One date written down wrongly shifts both drying off and calving preparation to the wrong day. We covered in detail how to catch the moment to inseminate in our insemination timing article.
What are the signs of pregnancy?
- Heat stopping: If the cow does not come into heat again after insemination (about 21 days later), the likelihood of pregnancy rises. This is the earliest clue.
- Behaviour and appetite: Settling down, a steadier appetite.
- Changes in the belly and udder: Growth in the belly in the later months, and filling of the udder towards the end.
- A fall in milk yield: In a milking cow, as pregnancy advances, and especially in the last months, milk yield falls more sharply than the normal lactation curve would suggest. On its own this is not proof, but if you have your milk records it is a sign worth noticing.
- Feeling movement in the last months: Late in pregnancy, with the cow standing and preferably before the morning feed, movement of the calf can be felt when you press a hand into the lower right flank. Not feeling it does not on its own mean she is not pregnant.
These signs are not enough for a definite diagnosis; that is made by veterinary examination.
Why are they not enough? Because every one of these signs can mislead. Some cows show heat behaviour even though they are pregnant; others are not pregnant but have a silent heat, so you never see it and conclude "she must have held". Heat can also stop in conditions such as inflammation of the uterus or an ovarian cyst. In other words, "I saw no heat" is a clue, not a diagnosis.
How is pregnancy confirmed?
- Rectal examination: By a veterinarian, usually ~6–8 weeks after insemination.
- Ultrasound: Gives an earlier and more detailed result (twins, viability of the foetus).
- Blood or milk tests: Laboratory tests that look for pregnancy proteins.
These three methods are not rivals but links that complete one another. The early methods buy you time: catch a cow that has not conceived early and you will not miss her next heat. The later methods give certainty. Decide together with your veterinarian which to use, according to the size of your herd and the facilities available.
| After insemination | What is done | What you learn |
|---|---|---|
| Day 18–24 | Heat observation (morning and evening) | If she has returned she is most likely not pregnant; a chance to inseminate again |
| Around 1 month | Ultrasound or a blood or milk test (if the vet thinks it appropriate) | An early sign of pregnancy; confirmation is needed for certainty |
| Week 6–8 | Rectal examination | Reliable confirmation of pregnancy |
| Month 5–6 | A second check | Whether the pregnancy is continuing |
| ~Day 220 | Drying off | Preparation for calving and the new lactation |
Step by step on the farm: how is pregnancy followed?
- Write down the insemination day the same day. Write it by reading the ear tag number, not as "the yellow cow". Note the bull or straw details and who inseminated her as well.
- Mark 21 days later on the calendar. Starting three days before that date and running to three days after it, that is through days 18–24, watch this cow with particular care.
- Observe heat morning and evening, outside milking. Watch quietly for 15–20 minutes while the animals are standing. The main signs are standing to be mounted, restlessness, a clear, stringy discharge, and rub marks at the tail head. A cloudy, foul-smelling or purulent discharge is not a sign of heat; if you see one, consult your vet before having her inseminated.
- If she returns, have her inseminated again straight away and record that date too. Knowing which insemination this is for a given cow will be useful to you later.
- Book the pregnancy check as an appointment. Draw up the list of cows to be checked before your veterinarian comes to the herd; a batch check is both cheaper and better organised than calling them out one at a time.
- Write the result in the book. As "pregnant", "empty" or "doubtful". For the doubtful ones, set a date for a re-check.
- Keep watching the cow as the pregnancy advances. If after confirmation you see heat behaviour, discharge or a sudden drop in milk, record it and tell your vet.
- Put the drying-off and calving dates on the calendar now. Getting ready when calving is upon you is already too late.
Common mistakes and how to spot them
- Not writing down the insemination date. This is the most expensive mistake. The sign: the answer to "when did we inseminate this cow?" being a guess. The result: a wrong calving date, late drying off, an unprepared calving.
- Treating day 21 as a single day. A return to heat generally spreads over days 18–24. If you only look on day 21 you will miss it. The sign: a month later, the situation of "we saw no heat, but she was not pregnant either".
- Assuming she is pregnant because no heat was seen. Silent heat is common, particularly in high-yielding cows and in the hot months. The sign: most of the cows found empty at the pregnancy check being recorded as "never showed heat".
- Putting the pregnancy check off for months. If an empty cow goes unnoticed for three months, for three months she eats feed and cannot start a new lactation. The sign: the calving interval lengthening in the fertility report.
- Getting one confirmation and never looking again. A pregnancy can be lost early on. Because the cow is recorded as pregnant, nobody watches for her heat and months go to waste. The sign: the calving date of a cow marked "pregnant" coming and going.
- Taking an early blood or milk test result as final. These tests are very valuable early on, but because of early embryonic loss vets generally want confirmation by examination.
- Keeping records without reading the tag. A pregnancy written against the wrong animal leads you to manage two animals wrongly at once. The sign: the date in the book not matching the state of the animal.
- Leaving the pre-calving ration to the last day. Feed changes are made gradually; an abrupt switch days before calving raises the risks. We described this transition in the ration calculation article.
- Leaving a pregnant heifer in the crowd of the herd. Heifers about to calve for the first time are more open to being pushed around; separate grouping pays off on the heifer rearing side.
When should a veterinarian be called immediately?
The situations below will not wait. Do not give medicine on your own; the medicine, the dose and the treatment decision belong to the veterinarian.
- Abortion: If a pregnancy is lost at any stage, report it at once. Some causes of abortion are diseases that can also pass to people and are notifiable. Do not touch the aborted calf or the membranes with bare hands, keep the area away from the other animals, and tell your vet.
- Foul-smelling, bloody or purulent discharge at any stage of pregnancy.
- A cow known to be pregnant coming into heat again and again — a sign that the pregnancy may no longer be continuing.
- Going off feed, a sudden drop in milk, weakness, difficulty standing especially in the last month of pregnancy.
- A marked departure from the expected calving date: If calving starts very early, or if there is no sign of calving at all well after the expected date has passed.
- If calving has started but is not progressing: If there is no progress despite straining after the water bag has appeared, or the calf's position looks wrong, do not lose time.
- If the afterbirth has not been dropped after calving consult your vet; if there is also loss of appetite, a bad smell or fever, call without delay.
The first hours after calving are critical for the calf as well; for the timing of colostrum and care in the first days, see our calf care: the first 30 days article.
Critical steps in the pregnancy calendar
- Insemination date — record it; it sets the expected calving date.
- Pregnancy check — a veterinary examination at about week 6–8.
- Drying off — stop milking about 60 days before calving.
- The pre-calving ration — adjust the feeding programme for the final period.
- Preparing for calving — a clean, quiet calving pen.
Drying off is the most neglected step in the pregnancy calendar. Stopping milking while milk is still coming feels hard, but the udder tissue renewing itself and the cow going into calving in good condition both depend on this period. We have gathered how it is done and what to watch for on the drying off page.
What good do records do?
Following a pregnancy is, from beginning to end, a matter of record keeping. There is no need to overstate it: keeping records does not get a cow in calf. But without records you cannot answer any of these questions:
- How many times has this cow been inseminated, and on what dates?
- How many days did she go empty after calving?
- How many cows in the herd are pregnant right now, how many empty, how many waiting to be checked?
- Which cows need to be dried off this month, and which need to calve?
- Which cow keeps failing to hold, and how much data is there for a decision to cull her?
The answers to these questions directly affect one of the herd's largest cost items: days spent empty. Every extra day a cow takes to get back in calf after calving is a day when the feed bill continues and the milk income does not arrive. Records make those days visible; what is visible can be managed. A notebook will do, so will a phone; what matters is that the same information always sits in the same place. You can find a practical road map for setting up that routine in the how to keep herd records article.
Records matter on the official side too: tagging calves and notifying the system, animal movements and support payments are tied to set periods and conditions. Practice on these matters is updated from time to time; for the exact periods, paperwork and programme, contact your provincial or district directorate of agriculture and forestry and your veterinarian.
A short checklist
- Have the insemination date and the ear tag number been written down?
- Has heat observation for days 18–24 been put on the calendar?
- Has a veterinary appointment been made for the pregnancy check?
- Has the result (pregnant / empty / doubtful) been entered in the book?
- Has the expected calving date been worked out?
- Has the drying-off date (about 60 days before calving) been set?
- Has the pre-calving feed transition been planned?
- Is the calving pen clean, dry and ready?
- Has a second check been made in mid-pregnancy?
- Are abortion, discharge or a sudden drop in milk being recorded?
Even hanging this list on the barn door helps. If you would rather keep it on a phone than on paper, we described where to start in the digitalisation on the farm article.
Do not miss a pregnancy or an insemination
Alprivo Herd Management reminds you automatically of insemination, pregnancy check and drying-off times, and works out the expected calving date.