Progesterone & Relaxin: Breeding Management Guide¶
Two hormones drive modern canine/feline breeding management: progesterone (ovulation timing) and relaxin (pregnancy confirmation). Both require quantitative, same-day results — the core strength of POCT.
Progesterone: Ovulation Timing¶
Progesterone is the gold standard for timing mating or artificial insemination. Serial measurement is essential — the trend identifies ovulation, not a single value.
| Progesterone (ng/mL) | Stage | Action |
|---|---|---|
| < 1 | Anestrus / early proestrus | Monitor |
| 1–2 | Approaching LH surge | Begin daily testing |
| 2–5 | Ovulation window | Breed / AI |
| > 5 | Post-ovulation | Confirm |
Progesterone Protocol¶
- Start day 5–7 of estrus.
- Test every 2–3 days until the rise begins.
- Test daily through the 2–5 ng/mL window.
- Breed/AI during the ovulation window.
Relaxin: Early Pregnancy Confirmation¶
Relaxin is produced by the placenta and confirms pregnancy:
| Timing | Finding |
|---|---|
| ~day 21–28 post-mating | Relaxin detectable |
| Pregnant | > 1.0 ng/mL |
Why Same-Day Results Matter¶
Breeding management is time-critical — a progesterone result that arrives days later from a send-out lab misses the ovulation window. Same-visit quantitative POCT lets you act in the same cycle.
FAQ¶
Why serial progesterone and not a single test? A single value cannot pinpoint ovulation; the trend across days identifies the pre-ovulatory rise and surge.
How early can relaxin confirm pregnancy? From ~day 21–28 post-mating.
What sample is used? Serum for progesterone; serum/plasma for relaxin (assay-dependent).
Case Study: Timing the Breeding¶
A breeder presents a 4-year-old bitch in estrus for ovulation timing.
- Day 6 of estrus: progesterone 1.8 ng/mL — approaching the LH surge.
- Day 8: progesterone 3.2 ng/mL — ovulation window approaching.
- Day 9: progesterone 5.4 ng/mL — post-ovulation; AI performed.
Outcome: A single timed insemination, confirmed by relaxin (> 1.0 ng/mL) at day 28.
Lesson: Serial progesterone — with same-day results — is what makes precise breeding management possible. A send-out lab result arriving days later would have missed the window entirely.
References¶
- Østergård Jensen S, Öberg J, et al. Validation of a dry-slide immunoassay for progesterone analysis in canine plasma in a clinical setting. Vet Clin Pathol. 2022;51(4):553-560. PMID: 35854401
- Nowak M, Boos A, et al. Luteal and hypophyseal expression of the canine relaxin (RLN) system during pregnancy: Implications for luteotropic function. PLoS One. 2018;13(1):e0191374. PMID: 29364921
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Authored by: Migibio Clinical & Scientific Affairs, Guangzhou Magic Biotech Co., Ltd.
Reviewed by: Migibio R&D Quality Committee
Last updated: 2026-08-13
Disclosure: Migibio (Guangzhou Magic Biotech Co., Ltd.) is the manufacturer of the FIA680/FIA880 analyzers and FICT reagents referenced in this content. See our Editorial & Review Policy.