A cow is in heat when she stands still and lets another animal mount her. That is the one sign you can trust. Clear, stringy mucus, restlessness and bellowing tell you heat is near. NDDB advises calling for artificial insemination (AI) about 12 hours after you first see heat: seen in the morning, inseminate in the evening; seen in the evening, inseminate the next morning.
- Heat comes back about every 3 weeks (18 to 22 days) and lasts less than a day, so it is easy to miss.
- Look twice a day, early morning and late evening. Most buffaloes come into heat at night.
- Standing to be mounted is the main sign. Mucus and restlessness alone are not enough.
- Use the morning-evening rule for AI, and let the technician or vet confirm the heat.
- No heat by 50 to 60 days after calving: call the vet.
What does a cow in heat look like?
Standing heat is the period when the cow can actually conceive. She holds still when another cow or a bull mounts her. Other signs come before and around it. NDDB lists these:
| Sign | What you see | How much it tells you |
|---|---|---|
| Standing to be mounted | She stays still while another animal mounts her | The surest sign: she is in heat now |
| Mounting others | She tries to ride other cows | Heat is near or started |
| Mucus | Clear, stringy mucus like egg white, hanging from the vulva or smeared on the tail | A good supporting sign |
| Behaviour | Restless, bellows often, sniffs and licks other cows, rests her chin on their backs | Supporting sign |
| Hair at the tail head | Hair roughed up or rubbed off where others mounted her | She has been mounted recently |
| Feed | Eats less than usual | Supporting sign |
| Bloody mucus | Mucus with blood, a few days later | Heat was a few days ago. Too late for this cycle |
Do not call for AI on mucus or restlessness alone. Inseminating at the wrong stage wastes semen, lowers the chance of pregnancy and raises the risk of infection, NDDB warns.
How long does heat last, and how often does it come back?
Heat is short. Vikaspedia says it lasts less than a day in cows and buffaloes, and comes back about three weeks later if the animal is not pregnant. ICAR's buffalo guidance gives these figures:
| Cow | Buffalo | |
|---|---|---|
| Cycle (heat to next heat) | About 3 weeks, give or take a day or two | 21 days (18 to 22) |
| How long heat lasts | Less than a day | About 21 hours (17 to 24); TNAU gives 12 to 18 |
| How clear the signs are | Usually clear | Weaker; mounting is much less common |
| When it starts | Any time of day | 60 to 70% between 6 pm and 6 am |
Because heat is short and the cycle is regular, a written date helps. If you saw heat on the 1st and she did not conceive, look hard around the 19th to the 23rd.
When should you call for AI?
NDDB's rule is to inseminate about 12 hours after you first see heat. TNAU explains why: the best conception comes when AI is done between the middle and the end of standing heat. Too early and the chance drops.
| You first see heat | Call for AI |
|---|---|
| Morning | Same evening |
| Evening | Next morning |
NDDB adds that the final decision should wait until the technician or vet confirms the stage of heat and the quality of the discharge by examining her. If heat lasts longer than usual, ask whether a second insemination is needed: TNAU notes two inseminations 12 hours apart are sometimes done.
Why buffalo heat is easy to miss
Buffaloes often show heat without clear signs. This is called silent heat, and Vikaspedia and ICAR both say it is common in buffaloes, especially high-yielding ones. Their behaviour is less intense than a cow's, they mount less, and most come into heat at night.
- Watch at night and dawn. ICAR says 60 to 70% of buffaloes come into heat between 6 pm and 6 am. Check late evening and before sunrise.
- Look closely at the vulva. A swollen, reddish vulva and mucus are often the clearest signs in a buffalo.
- Expect more silent heat in summer. A study of Murrah buffaloes found silent heat and night-time heat become more common in summer. Shade, water and cooling help.
- Use a teaser bull if your village or dairy has one. TNAU suggests teaser bulls for finding silent or weak heat.
- Write down every sign, even a weak one. A weak sign on a date tells you when to look next cycle.
After calving: when should she come back into heat?
The Dairy Knowledge Portal (NDDB) says a cow normally comes into heat within 45 days of calving. Breed her at the next heat after that first one, or within 60 to 90 days of calving. TNAU says a cow that shows no heat by 50 days usually has a problem and needs examining; the Dairy Knowledge Portal puts the limit at 60 days. Either way, do not wait months.
After AI, watch for heat again around 3 weeks later. A cow that comes back into heat did not conceive. TNAU advises a pregnancy check 45 to 60 days after service, so a cow that is not pregnant can be bred again quickly. To work out her calving date and when to dry her off, use the cow pregnancy calculator.
What if she does not come into heat?
First check feeding. TNAU notes an animal may not come into heat if it lacks feed, protein, minerals and salt, or water. In summer, heat stress makes heat harder to see, especially in buffaloes, so keep them in shade with plenty of water. Then check whether you are looking at the right times: many missed heats are simply not seen.
If there is still no heat by 50 to 60 days after calving, or a cow keeps coming back into heat after AI, call your vet. These need an examination, not guesswork. Do not give hormones or medicines on your own.
What to do this week
- Set two fixed heat checks a day: before the morning milking and after dark. For buffaloes, add a check at night if you can.
- Teach whoever milks to report standing heat, clear mucus and bellowing the same hour they see it.
- Write down the date and time of every heat sign and every AI, with the technician's name and the semen or bull ID.
- Mark the date 3 weeks after each AI and look for heat around it. Book a pregnancy check for 45 to 60 days after AI.
- List cows that calved more than 60 days ago and have shown no heat, and show them to your vet.
This is easier when the record is made in the shed. In Pashupaalak, a milker can log a heat sign (standing heat, mucus, restlessness or mounting) from the worker app, the AI technician logs the insemination with the semen ID, and pregnancy checks show up in your due list. It works in Hindi, Marathi and English, on the web now, with the Android app coming soon. If you already keep daily dairy records, add heat signs to them.
