Why use a defined season
South Dakota State University Extension points to a breeding season of about 64 days. A cow comes into heat every 21 days, so 64 days gives three chances to settle. The benchmarks it cites are 65% of cows bred by day 21, 90% by day 42 and 95% by day 64. A short calving season means fewer weeks of night checks, a more even calf crop and easier health and feeding plans.
Bull turnout to calving
Cows calve about 283 days after breeding. This table uses 2026 as the breeding year and a 64 day breeding season:
| Bull in on | Bull out on | First calves due | Last calves due |
|---|---|---|---|
| Mar 1, 2026 | May 4, 2026 | Dec 9, 2026 | Feb 11, 2027 |
| Apr 1, 2026 | Jun 4, 2026 | Jan 9, 2027 | Mar 14, 2027 |
| May 1, 2026 | Jul 4, 2026 | Feb 8, 2027 | Apr 13, 2027 |
| Jun 1, 2026 | Aug 4, 2026 | Mar 11, 2027 | May 14, 2027 |
| Jul 1, 2026 | Sep 3, 2026 | Apr 10, 2027 | Jun 13, 2027 |
Individual cows calve earlier or later than 283 days. Breed shifts it, from about 279 days for Holstein and Jersey to 292 for Brahman, so see the cow gestation calculator for your breed, and the cow gestation chart for a date for every breeding date.
Calendar for one cow
| Event | When | Example if bred Jun 1, 2026 |
|---|---|---|
| Pregnancy check | About day 45 | Jul 16, 2026 |
| Dry off a dairy cow | About day 220, roughly 60 days before calving | Jan 7, 2027 |
| Move to the calving area | About day 253 | Feb 9, 2027 |
| Expected calving | Day 283 | Mar 11, 2027 |
| Rebreed by | About 80 days after calving, to keep a yearly calf | May 30, 2027 |
SDSU advises that cows be bred within 80 days after calving to keep a calf a year, and that cows typically begin cycling again 40 to 60 days after calving.
Before the first calf
- Set up a clean, dry calving area where you can watch cows, and check heifers more often than mature cows.
- Have your vet's number, and an emergency number, written where you can find them.
- Know when to call: a cow in hard labor that is not making progress, or a calf that is malpositioned.
- Plan for a calf to get colostrum, the first milk, soon after birth.
Frequently asked questions
How long is a calving season?
A 64 day breeding season produces a calving window of about nine weeks, 283 days later.
When should I turn the bull out?
Count back 283 days from the date you want the first calf. Turning the bull out on Jun 1, 2026 gives first calves around Mar 11, 2027.
When should a cow be rebred after calving?
Within about 80 days, to keep a calf every 12 months.