Progesterone Testing for Canine Breeding Timing
· By Dr. Tang
TL;DR: Progesterone timing is a serial measurement, not a single snapshot. The reference points are ~2–3 ng/mL (LH surge), ~5 ng/mL (ovulation), and 8–15 ng/mL (optimal breeding window). Test every 1–3 days, watch the rate of rise — a slow climber with frozen semen averages fewer puppies — and remember that a quantitative number, not a strip, is what pins down a window measured in hours.
Progesterone timing is the foundation of canine breeding, and it’s deceptively simple: measure the hormone, watch it rise, breed at the right moment. The simplicity hides the precision that separates a full litter from a missed cycle.
The Progesterone Timeline
Progesterone rises through the canine cycle in a predictable pattern. The reference points, drawn from large-scale clinical studies and specialist guidance:
| Progesterone | Clinical meaning |
|---|---|
| <1 ng/mL | Baseline — too early |
| 1.5–2.0 ng/mL | Initial rise, coinciding with the LH surge |
| 2.0–3.0 ng/mL | LH surge (a large-scale study found a mean of 2.7 ng/mL) |
| 4–10 ng/mL | Ovulation (many bitches ~5 ng/mL) |
| 8–15 ng/mL | Optimal breeding window |
| >20 ng/mL | Late fertile period — may need TCI or surgical insemination |
Two timing facts anchor the whole protocol:
- Ovulation follows the LH surge by roughly 48–72 hours.
- The bitch ovulates immature oocytes that need another 48–72 hours to mature — so the true fertile window is four to six days after the LH surge.
The Serial Protocol
Because the rise is gradual, a single measurement is nearly useless — you need the trend. The standard protocol:
- Start around day 5 of heat, or when vaginal cytology shows the onset of oestrus.
- Test every 1–3 days.
- Increase frequency to daily as the rise accelerates.
The reason for daily testing late in the cycle: once progesterone passes ~4 ng/mL, a 24-hour jump of 3–4 ng/mL or more confirms ovulation. Some bitches jump as much as 8–10 ng/mL in a day. If you’re only testing every three days, you can sail right past the window and never know.
The Slow-Rise Trap
Some bitches stall — sitting at 2.5–4.0 ng/mL for several days before continuing to climb. This “stall” is a genuine clinical phenomenon, and it’s where naive timing goes wrong.
The stakes of a slow rise were quantified in a study of over 1,400 breeding cycles: a slow progesterone rise paired with frozen semen produced an average of 3.9 puppies, versus 5.6 with a fast rise.
The takeaway for practice: track the rate of rise, not just the absolute value. A bitch whose progesterone climbs slowly may need a different insemination plan — or a switch from frozen to a more forgiving semen type — than one that surges.
Semen Type Sets the Precision Bar
Why all this precision? Because the type of semen dictates how forgiving your timing can afford to be:
| Semen type | Survival in the bitch | Timing tolerance |
|---|---|---|
| Fresh | 4–6 days | Forgiving — a day off still works |
| Chilled | ~3 days | Moderate |
| Frozen | ~12 hours | Unforgiving — near-exact timing required |
For a natural breeding with fresh semen, an approximate window is fine. For frozen semen — with a 12-hour survival window and a target of 10–20 ng/mL — only a precise quantitative number will do.
The Unit Trap
Different analyzers and labs report progesterone in different units, and a misread unit is a misread cycle. The conversion:
ng/mL × 3.18 = nmol/L
nmol/L ÷ 3.18 = ng/mLBefore you interpret any value, confirm which unit it’s in. A “5” in ng/mL means ovulation; a “5” in nmol/L means roughly 1.6 ng/mL — still early. The distinction is the difference between breeding today and breeding next week.
Why Quantitative Beats Qualitative Here
Progesterone timing is the cleanest demonstration of why quantitative matters. The decisions hinge on distinctions of 2–3 ng/mL:
- 2 ng/mL → “not yet”
- 5 ng/mL → “ovulation”
- 8 ng/mL → “breed now”
A colour-change strip cannot make these distinctions. A semi-quantitative kit gives broad bands (low/medium/high) — and, critically, is often capped at 5 ng/mL, which the literature notes makes it “considerably reduced” in usefulness for frozen-semen work, where you need to read 10–20 ng/mL (PMC8924395).
An in-house quantitative immunoassay analyzer returns the actual number in minutes, letting you time insemination the same day instead of waiting 24–72 hours for a reference lab — a delay that can miss a fast-moving window entirely.
Application & Commercial Angle
Who should care: breeders and reproductive veterinarians. The protocol turns breeding timing from guesswork into a repeatable, billable service.
In practice, serial progesterone is the clinic’s recurring revenue anchor: each cycle involves several timed draws, and the breeder stays with the clinic that can read the rise — not just a positive strip.
FAQ
What progesterone level indicates ovulation in dogs?
Ovulation occurs when progesterone reaches roughly 4–10 ng/mL, with many bitches ovulating around 5 ng/mL. This follows the LH surge, when progesterone first rises to about 2–3 ng/mL, by roughly 48–72 hours.
What progesterone level is the optimal breeding window?
The optimal breeding window is commonly placed at 8–15 ng/mL, roughly four to six days after the LH surge, once the ovulated oocytes have matured. Some sources extend the fertile period to 15–40 ng/mL at peak.
How often should I test progesterone during a cycle?
Start around day 5 of heat and test every 1–3 days, increasing frequency as the rise approaches. Once progesterone passes ~4 ng/mL, a 24-hour jump of 3–4 ng/mL or more confirms ovulation, so daily testing becomes valuable at that point.
Does the rate of progesterone rise matter?
Yes — over 1,400 cycles show the rate matters: a slow rise with frozen semen averaged 3.9 puppies versus 5.6 with a fast rise. Track both the value and the rate of change.
How do I convert progesterone units?
ng/mL × 3.18 = nmol/L, and nmol/L ÷ 3.18 = ng/mL. Always confirm which unit your analyzer or lab reports before interpreting a value.
Can I time breeding with a semi-quantitative progesterone kit?
For 2 semen types the answer changes: fresh-semen natural breeding can use a broad-band kit to schedule a veterinary blood draw, but chilled or frozen semen demands quantitative precision — semi-quantitative kits often cap at 5 ng/mL while frozen-semen timing needs 10–20 ng/mL.
Key Takeaways
- Progesterone timing is a serial trend, not a snapshot — test every 1–3 days, daily late in the cycle.
- Reference points: LH surge ~2–3 ng/mL, ovulation ~5 ng/mL, optimal window 8–15 ng/mL.
- A 24-hour jump of 3–4 ng/mL after ~4 ng/mL confirms ovulation.
- The rate of rise predicts litter size — a slow rise with frozen semen averaged 3.9 puppies vs 5.6.
- Confirm units (ng/mL vs nmol/L) and use a quantitative method — semi-quantitative kits cap at 5 ng/mL.
References
- dvm360. Breeding Management 102 — It’s All in the Timing (Proceedings). https://www.dvm360.com/view/breeding-management-102-its-all-timing-proceedings
- Kunanusont N, Punyadarsaniya D, Ruenphet S. Accuracy and precision guidelines for optimal breeding time in bitches. Vet World. 2021;14(3):585–588. doi:10.14202/vetworld.2021.585-588
- Comparison of three progesterone quantification methods using blood samples drawn from bitches during the periovulatory phase. PMC8924395.
This content is for educational and product-selection purposes only. It is not a substitute for veterinary diagnosis — any animal with suspected disease should be evaluated by a veterinarian. Reference ranges are assay-dependent; always use your analyzer’s validated intervals. Product specifications are as published by Migibio (Guangzhou Magic Biotech Co., Ltd.) and may change.