Canine Progesterone and Relaxin Testing for Breeding

For dog breeders, timing is everything. Whether breeding naturally or via artificial insemination, success hinges on precisely identifying ovulation and confirming pregnancy. Two biomarkers — progesterone and relaxin — make this possible with quantitative point-of-care testing. This guide explains how to use them.

Progesterone: Timing Ovulation

Why It Matters

Canine reproduction has a unique challenge: the bitch ovulates immature oocytes that require 2–3 additional days to mature and become fertilisable. Timing insemination to this window is the single most important factor in breeding success.

Progesterone measurement tracks the oestrous cycle with precision, because progesterone rises in a predictable pattern around ovulation.

How to Use It

1. Begin testing a few days after the start of oestrus (or when the bitch first accepts the male).
2. Test every 1–2 days as progesterone begins to rise.
3. Identify the surge — progesterone rising above a threshold (typically ~2 ng/mL, or 4–6 ng/mL depending on the reference used) marks ovulation.
4. Time breeding — natural mating or artificial insemination is performed 2–4 days after the progesterone surge, when oocytes are mature.

Why Quantitative Testing Is Essential

Progesterone values rise from baseline (<1 ng/mL) through ovulation (2–10+ ng/mL) to luteal-phase highs. This is a continuum, not a yes/no — only a quantitative test can pinpoint where the bitch is in the cycle. Visual (qualitative) tests cannot provide the precise timing that modern breeding demands.

Related product: Canine Progesterone Test

Relaxin: Confirming Pregnancy

Why It Matters

After breeding, the next question is: “Did it take?” Relaxin — a hormone produced by the developing placenta — provides the answer.

How to Use It

• Test from ~day 21–28 post-ovulation (relaxin becomes reliably detectable).
• A positive result confirms pregnancy.
• A negative result suggests non-pregnancy or testing too early — repeat if in doubt.

Why Relaxin Beats Other Methods

• Distinguishes true pregnancy from pseudopregnancy — a common source of confusion in bitches.
• Non-invasive — a simple blood test, no imaging equipment needed.
• Early — earlier than reliable palpation or radiography.

Related product: Canine Relaxin Test

The Breeding Workflow

A complete, modern breeding programme uses both biomarkers:

1. Progesterone — to time ovulation and insemination precisely.
2. Relaxin — to confirm pregnancy ~3–4 weeks later.
3. (Optional) imaging — ultrasound or radiography for litter confirmation and count.

Benefits of Point-of-Care Testing for Breeders

• Speed — results in minutes, enabling same-day breeding decisions.
• Precision — quantitative values, not guesses.
• Convenience — no laboratory delay for time-sensitive ovulation timing.
• Cost-effectiveness — reduced repeat-breeding cycles and missed opportunities.

In the Bigger Picture

Progesterone and relaxin are part of the broader biomarker toolkit. For a full overview, see Veterinary Biomarker Monitoring.

Conclusion

Quantitative progesterone and relaxin testing has transformed canine breeding from an art into a science. By timing ovulation precisely and confirming pregnancy early, breeders can maximise litter success and reduce the uncertainty that has long plagued the field.