Understanding the canine heat cycle: timing the perfect mating

If you plan to breed, the heat cycle is the calendar everything else hangs on. Misread it and you miss the window entirely. The good news: it follows four predictable stages.

The four stages

1. Proestrus (≈ 9 days)

The visible start of the season: a swollen vulva and bloody discharge. Males are very interested, but the bitch is not yet receptive and not fertile. Progesterone is still low.

2. Estrus (≈ 9 days)

The fertile stage. Discharge lightens to straw-coloured, the bitch becomes receptive and "flags" (moves her tail aside). Ovulation happens early in estrus, and because eggs need ~2 days to mature, the best conception comes from breeding a couple of days after ovulation.

3. Diestrus (≈ 60 days)

The cycle winds down whether or not she conceived. Progesterone stays elevated for weeks — which is why a false pregnancy can look convincingly real.

4. Anestrus (≈ 4 months)

The resting phase between seasons. Most bitches cycle roughly twice a year, though it varies by breed and individual.

Why behaviour alone isn't enough

Receptive behaviour overlaps the fertile window but doesn't pinpoint it. A bitch can stand for a male before and after her most fertile days. To breed with confidence you need to know when she ovulated — and that means measuring hormones, not watching the tail.

Timing it properly

The reliable workflow is:

1. Note day 1 as the first day of bleeding.
2. Begin progesterone testing from around day 5–7.
3. Track the rise to confirm ovulation (~5 ng/mL).
4. Plan the mating ~2 days later.
5. Count 63 days from ovulation for an accurate due date.

Record everything

Cycle length, stage dates, behaviour and test results all feed next time's plan — bitches tend to repeat their own pattern. Combine careful cycle tracking with health-tested, well-matched parents (your pedigree certificate is part of that picture) and you give every planned litter the best possible start.