Breed a heifer when she is big enough, catch every heat, have her inseminated at the right time, and ask a vet to confirm the pregnancy. The aim is a calf every 12–14 months from a cow and every 13–15 months from a buffalo (NDDB, NDDB).
First breeding: weight before age
NDDB advises breeding a heifer only when she reaches about 55–60% of her expected adult weight (NDDB):
| Heifer | Breed her at about | Target age at first calving |
|---|---|---|
| Native cow | 180–220 kg | 30–36 months |
| Jersey crossbred | 250–300 kg | 24–30 months |
| HF crossbred | 300–350 kg | 24–30 months |
| Buffalo | 300–350 kg | 30–36 months |
- A healthy crossbred heifer should come into heat by about 18 months; buffaloes and local breeds take longer, around 24 months (NDDB).
- Feed growing heifers well: about 1.5–2 kg of concentrate a day, so that they gain 500–700 g a day (NDDB).
- In breed records many buffaloes have their first calf only at about 3.5–4 years (NBAGR database); NDDB's 30–36 months is a target with good feeding and care.
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Heat signs and the time for AI
A cow or heifer that is not pregnant comes into heat about every 21 days (18–24). Heat lasts about a day, and the standing heat 12–18 hours (NDDB, TNAU). Signs (NDDB):
- she stands still when another animal mounts her: the surest sign;
- she mounts others, is restless and bellows often;
- clear, stringy mucus hangs from the swollen, red, moist vulva;
- she urinates often and raises her tail;
- she eats less, and her milk drops for a while.
When to inseminate:
- Watch for heat in the early morning and late evening (NDDB).
- Heat seen in the morning: AI the same evening. Heat seen in the evening: AI the next morning (NDDB).
- If you do not know when the heat began, have her inseminated within 6 hours of first seeing it, or while she is in standing heat. In hot weather, choose the late evening or early morning (NDDB).
- One AI per heat is usually enough. A second is needed only if a trained inseminator finds her still in standing heat (NDDB).
Buffaloes: silent heat
- Buffaloes do not mount others or stand to be mounted, the mucus is often scanty, and some, especially high yielders, do not bellow (TNAU).
- Look instead for a swollen vulva that looks oily, teats that swell with held-back milk, frequent spurts of urine that leave a white mark below the vulva, restlessness, going off feed and a raised head (TNAU).
- 60–70% of buffaloes come into heat between 6 pm and 6 am, so watch them in the evening and early morning (TNAU).
- In summer many buffaloes show no heat at all. In studies ICAR-CIRB cites, wallowing and showers in the hot hours raised conception; feed roughage at night, with green fodder, mineral mixture and water whenever she wants (ICAR-CIRB).
- AI works as well in buffaloes as in cows when the heat is caught in time (NDDB).
AI at the hospital or at your door
- In Tamil Nadu, AI is given at veterinary dispensaries and sub-centres, by mobile veterinary units (Tamil Nadu), and through milk societies to their members (Dairy Policy Note).
- On 25 October 2026, the national AI programme was bringing AI to farmers' doors free of charge in 13 Tamil Nadu districts (Tamil Nadu, PIB). See the list in Dairy farming loans, insurance and schemes in 2026, and ask your vet what applies elsewhere.
- Ask the technician the breed of the semen, the exotic blood level for crossbreds, and the bull's details. Semen should come from an A- or B-graded semen station and suit your state's breeding policy (NDDB).
- For a local cow of no fixed breed, NDDB suggests semen of native dairy breeds such as Sahiwal, Gir or Red Sindhi; HF or Jersey semen only if you can keep a crossbred and the state policy allows it (NDDB). More in Choosing a dairy cow or buffalo: breeds compared.
Sexed semen
- Sexed semen gives mostly female calves: in Tamil Nadu in 2025–26, 88.9% of the calves born from it were female, about 9 in 10 (Tamil Nadu). It is never a guarantee.
- Conception can be lower than with ordinary semen. NDDB advises using it mainly in heifers, or in cows up to the third lactation with a good breeding record (NDDB).
- More female calves means fewer difficult births, which matters most for first-calf heifers (NDDB).
- Ask your vet about the cost and any government help, and see Dairy farming loans, insurance and schemes in 2026.
Pregnancy check and dry period
- If she does not come back into heat 18–21 days after AI, she may be pregnant; if she does, have her inseminated again (NDDB).
- A vet can confirm the pregnancy from about 45–60 days after AI (TNAU, NDDB).
- Not pregnant after 3 inseminations, though she comes into heat normally? Ask the vet to examine her (NDDB).
| Pregnancy lasts | Dry period before calving | |
|---|---|---|
| Cow | 280–290 days | About 2 months |
| Buffalo | 305–318 days | 2–3 months |
Pregnancy lengths are from TNAU (TNAU); the dry periods from NDDB and TNAU (NDDB, TNAU).
- NDDB advises drying a cow off within 15 days after the 7th month of pregnancy. For a high yielder, start 2 weeks before: cut the concentrate and feed mainly dry fodder, milk once a day for a week, then every other day, then stop. Never cut her water, and look at her udder every day after (NDDB).
- Feeding in late pregnancy is in Dairy cow feeding: fodder, concentrate, minerals and water.
Calving: when to call the vet
- About 2 weeks before she is due, move her to a clean calving pen. Or tie her apart on clean, dry ground with straw 4–5 days before, and watch her closely for the last 1–2 days (NDDB).
- Signs that calving is near: the udder fills and may drip milk, and about a day before, hollows appear on both sides of the tail head (TNAU). Within 24 hours she gets up and lies down often, raises her tail, kicks at her belly and has a sticky discharge (NDDB).
- In about 95% of calvings, the calf comes forward, head between its front legs (ICAR-CIRB).
Call the vet at once if:
- the calf is not out within about an hour after the water bag bursts (heifers can be slower), or only the head or one leg shows (NDDB);
- a buffalo looks ready to calve but no water bag appears, and she is restless and kicks at her belly: her womb may be twisted (ICAR-CIRB);
- the afterbirth is not out by 12 hours (it usually comes out within 3–8 hours) (NDDB, ICAR-CIRB);
- the womb comes out: keep it clean and off the ground, and do not push it back (NDDB).
Do not pull the calf or the afterbirth, and do not put your hand inside her: wait for the vet. Milk her, or let the calf suckle, even before the afterbirth comes out (TNAU). For the newborn calf, see Calf care: colostrum, milk feeding, weaning and pens.
Back in calf
- A cow should come into heat 30–60 days after calving, a buffalo 45–90 days (NDDB).
- Breed a cow at the heat after her first one, or 60–90 days after calving (NDDB). Buffaloes usually conceive later, by 90–150 days (NDDB).
- Call the vet if there is no heat by 60 days after calving, or a bad-smelling, red-brown or white discharge after 21 days (NDDB).
- Write down every heat, AI date and bull number, pregnancy check, due date, drying-off date and calving. The dates tell you when to watch for heat and when she is due.
Common mistakes
- Breeding a heifer that is too small.
- Missing heats because nobody watches in the early morning and late evening.
- Inseminating too early or too late.
- Not having a vet confirm the pregnancy.
- Pulling the calf or the afterbirth instead of calling the vet.
Frequently asked questions
When can a heifer be bred for the first time?
When she reaches about 55–60% of her adult weight: about 250–300 kg for a Jersey crossbred, 300–350 kg for an HF crossbred or a buffalo, and 180–220 kg for a native heifer, as per NDDB.
How long is a cow pregnant?
About 280–290 days. A buffalo carries her calf longer, 305–318 days.
Does sexed semen always give a female calf?
No. In Tamil Nadu about 9 in 10 calves from sexed semen were female in 2025–26, and conception can be lower than with ordinary semen.
How soon after calving can I breed her again?
From about 60–90 days after calving for a cow, at the heat after her first one. Buffaloes often take longer.
Next
Get ready for the newborn with Calf care: colostrum, milk feeding, weaning and pens, and feed the pregnant animal well with Dairy cow feeding: fodder, concentrate, minerals and water. Keep vaccinations up to date with Cow and buffalo health: vaccine calendar and warning signs. Looking for a heifer or a cow in calf? See cows for sale and buffaloes for sale, and check each animal before you pay (How to buy a milch cow or buffalo: checks and papers).