The Canine Heat Cycle: A Practical Timeline for Breeders
Proestrus, estrus, diestrus, anestrus — what actually happens in each stage, how long each one lasts, and how to time a breeding with confidence.
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Every experienced breeder eventually learns the same lesson: the calendar is a guide, the individual dog is the truth. Still, the canine estrous cycle follows a well-documented rhythm, and knowing that rhythm cold is what lets you spot when a particular girl is early, late, or textbook.
Here's the practical version — what happens in each stage, what you'll actually observe, and where the fertile window really sits.
The four stages at a glance
A complete cycle averages about six months, though anywhere from four months to a year can be normal for an individual dog. Small breeds often cycle more frequently; giant breeds sometimes only once a year.
| Stage | Typical length | What's happening |
|---|---|---|
| Proestrus | ~9 days (3–17) | Swelling and bloody discharge; males interested, female not receptive |
| Estrus | ~9 days (3–21) | Discharge lightens; female receptive — this is the breeding window |
| Diestrus | ~2 months | Hormonal pregnancy state whether bred or not |
| Anestrus | ~4 months | Reproductive rest before the next cycle |
Proestrus: the countdown starts
The first day you notice a swollen vulva and bloody discharge is day one — write it down, because every other estimate keys off this date. During proestrus, estrogen is climbing, males become very interested, and the female firmly declines. Expect around nine days, but anywhere from three days to over two weeks is within normal range.
What to record
Day one of visible signs, her behavior, and anything unusual compared to her last cycle. Cycle-to-cycle patterns are the most reliable predictor a breeder has — a girl who runs long tends to keep running long.
Estrus: the window that matters
When the discharge lightens from red toward straw-colored and she starts flagging — tail to the side, standing for the male — she's in estrus. Ovulation typically happens early in this stage, but eggs need another two to three days to mature after release, which is why days 10–14 from the start of the cycle are the classic peak-fertility guideline.
The guideline is a starting point, not a guarantee. Individual dogs ovulate anywhere from day 5 to day 30 of their cycle.
Why progesterone testing wins
Serial progesterone tests through your veterinarian are the gold standard for timing. Baseline progesterone rises with the LH surge, and your vet can pinpoint ovulation within about a day — which matters enormously for chilled or frozen semen, where the viable window is short. If you're shipping semen or doing a transcervical insemination, test; don't guess.
Diestrus: pregnant either way (hormonally)
After estrus ends, progesterone stays high for about two months whether or not the breeding took. This is why false pregnancies are common and why a girl can look and act pregnant without being so. If she was bred, this is gestation — about 63 days from ovulation.
Anestrus: the reset
Roughly four months of reproductive quiet while her body recovers. Nothing to do here except normal conditioning: weight, coat, and any health testing you want current before the next cycle.
Putting it to work
Three habits separate breeders who time well from breeders who scramble:
- Record day one, every cycle. The average interval between her own cycles beats any breed average.
- Watch for her pattern. Two or three recorded cycles reveal whether she runs 5½ months or 8.
- Confirm with progesterone. Especially for anything other than live cover with an experienced stud.
Whelpify's heat cycle tracking does the record-keeping half automatically — log day one, and it learns each girl's personal rhythm, projects her next heat on a shared calendar, and reminds you two weeks out. The progesterone half still belongs to your vet.