Cattle · 8 min read
Cattle Breeding Calendar: From Service Date to Calving Date
Updated 7 August 2026
Cattle breeding runs on two numbers: a 21-day oestrous cycle and a 283-day gestation. Everything else on a cattle breeding calendar — heat checks, pregnancy diagnosis, dry-off, calving pens — is scheduled off the service date using those two.
This calendar lists what happens when, in the order it happens, with the dates a herd manager needs to diary.
When is a cow ready to breed again?
A cow cycles every 21 days on average, with a normal range of 18 to 24 days. Standing heat lasts 12 to 18 hours, and ovulation follows about 10 to 14 hours after it ends — which is why the classic rule is to serve a cow seen in standing heat in the morning that same afternoon.
After calving, allow a voluntary waiting period of 50 to 60 days before the first service so the uterus has recovered. First heats usually appear from about day 30, but conception rates before day 50 are poorer.
- Cycle: 21 days (18–24).
- Standing heat: 12–18 hours.
- Best service window: 12 hours after standing heat begins.
- Voluntary waiting period after calving: 50–60 days.
- Heifers: breed at 60–65% of mature bodyweight, typically 13–15 months.
How long are cows pregnant?
Average gestation in cattle is 283 days, with a normal range of 279 to 287 days. Breed shifts the average: Jersey and Angus tend to run slightly shorter, Brown Swiss, Charolais and Brahman-influenced cattle slightly longer. Bull calves and twins also move the date.
For planning, use 283 days for the due date and treat 279 days as the date the calving pen must be ready.
| Breed | Typical gestation |
|---|---|
| Holstein | 278–280 days |
| Jersey | 279 days |
| Angus | 279–283 days |
| Hereford | 285 days |
| Brown Swiss | 290 days |
| Brahman | 292 days |
Breed averages from published herd records; individual cows vary by several days.
What is the cattle breeding timeline after service?
| Days after service | What happens | Action |
|---|---|---|
| 18–24 | Return to heat if not pregnant | Watch closely; re-serve if seen |
| 28–35 | Earliest ultrasound | Scan or blood/milk PAG test |
| 35–45 | Rectal palpation possible | Confirm pregnancy |
| 60–90 | Recheck for early embryonic loss | Second confirmation |
| 150 | Second trimester begins | Rising nutritional demand |
| ~223 (60 days out) | Dry off dairy cows | Dry cow ration, teat sealant |
| ~262 (21 days out) | Move to transition group | Close-up ration |
| 279–287 | Calving | Calving pen, monitor, colostrum plan |
How do you catch heats reliably?
Most calving-interval problems are heat detection problems, not fertility problems. If less than 50% of expected returns are being seen, fix detection before changing bulls or semen.
- Observe for 20–30 minutes at least twice daily, away from feeding times.
- Standing to be mounted is the only definitive sign; chin resting and restlessness are precursors.
- Tail paint, heat mount detectors or activity collars catch the night heats visual checks miss.
- Record every heat: a cow with no recorded heat 24 days after service is either pregnant or being missed.
How do you work out a calving date from a service date?
Take the service date, add 283 days, then bracket it by four days each way.
A cow served on 15 April is due 23 January the following year. Expect calving any time from 19 to 27 January, dry her off around 24 November, and move her to the close-up group about 2 January. If she was not held, she should show heat again around 6 May.
What changes in the last trimester?
- Roughly 70% of fetal growth happens in the final third of gestation.
- Dairy cows are dried off about 60 days before the due date to rebuild udder tissue.
- Body condition score at calving should be about 2.5 to 3.0 (5-point scale) — over-fat cows have harder calvings.
- Vaccination and mineral programmes are timed to the due date so colostrum carries the right antibodies.
Which calculator should you use next?
- Cow due date calculatorAverage 283 days
- Water buffalo due date calculatorAverage 310 days
- Goat due date calculatorAverage 150 days
- Sheep due date calculatorAverage 147 days
More species are listed on the full gestation chart and in the guides index.
Common questions
Figures here are published reference ranges for planning, not veterinary advice. Confirm pregnancies and health decisions with your own vet.