When is a dog fertile? Ovulation and the best mating days
The most common misjudgement about the heat: “She is hardly bleeding any more, the worst is over.” In fact the fertile days begin exactly then. For owners this means: be careful in the second half of the heat. For breeders it means: find the ovulation, don't count the bleeding.
What happens in the body
Proestrus with its bleeding is preparation. Only when the dog accepts the male does standing heat begin. At about the same time, on average a day earlier, comes the LH surge, the hormone pulse that triggers ovulation. About two days after the LH surge the eggs are released. Unlike in humans they cannot be fertilised yet: they mature for another two to three days and are then fertile for two to three days.
Sperm survive in the dog for up to a week. So a mating several days before ovulation can lead to a pregnancy, and so can a mating in the first days of diestrus.
The rule of thumb “day 10 to 13” and why it often fails
Counting from the first day of bleeding, the best mating days are on average day 10 to 13. But according to data from university clinics that is true for only about 40 percent of dogs. Around 10 percent are ready earlier, half later, some only on day 20 or beyond. The reason: proestrus lasts anywhere from 3 to 17 days, and nobody can tell from the outside how long it will be this time.
For owners who want to prevent a pregnancy this means: the whole heat counts as risky, especially from the moment the discharge turns lighter and the dog flags her tail. Stay careful for another two days after she stops standing.
The signs of standing heat
- Discharge turns lighter, pinkish to straw-coloured, and less
- The vulva softens
- She stands for the male, flags her tail to the side, presents herself
- When touched above the tail she goes still and lifts the vulva
- She actively seeks contact, pulls on the leash towards males, tries to run off
The tail test works without a male: stroke your hand along her back towards the tail. If she moves the tail to the side and stands still, she is in standing heat.
For breeders: progesterone instead of the calendar
Only a progesterone test in the blood shows ovulation reliably. First test around day 5 to 7 of the heat, then every two days until the value rises clearly.
| Progesterone (ng/ml) | Meaning |
|---|---|
| below 1.5 | baseline, not yet |
| about 2 | LH peak, ovulation follows in 2 days |
| about 5 (4 to 8) | ovulation |
| 10 to 20 | eggs mature, best mating days |
| above 25 | window closing, usually too late |
Conversion for laboratories that report in nmol/l: 1 ng/ml = 3.18 nmol/l.
The best mating days with fresh semen are two to four days after ovulation, with frozen semen day 5 to 6 after the LH peak, because thawed sperm survive only briefly. Two matings two days apart increase the chance.
Knowing the ovulation also means knowing the due date: 63 days after ovulation, usually accurate to a day or two. Counted from the mating the date varies by a week, precisely because sperm survive for days.
What Lunella does with this
Lunella first calculates the fertile days from the start of standing heat, which you record with a tap on “Standing today”. In breeder mode the app takes the progesterone values from the daily observations, sets ovulation automatically, shows the best mating days and calculates the due date from ovulation. You can send the report with all values to the practice as a text file.
In short: a dog is fertile in standing heat, when the bleeding turns lighter and she accepts the male. The rule of thumb “day 10 to 13” fits fewer than every second dog. For breeding only ovulation counts, and progesterone shows it.
This article does not replace veterinary advice. If your dog shows signs of illness, see your vet.
