An Overview on LH Testing

Breeding dogs using frozen semen requires precise timing to maximize conception rates. Unlike fresh or chilled semen, frozen semen has a much shorter lifespan (12-24 hours once thawed and inseminated), making it critical to inseminate at the exact moment the eggs are mature and ready for fertilization.

The most reliable way to determine this timing is through luteinizing hormone (LH) testing. Understanding the science behind LH testing and learning how to accurately detect the surge will significantly improve success rates when using frozen semen.

Understanding the Canine Reproductive Cycle
A female dog goes through four stages in her reproductive cycle:
1. Proestrus – Lasts 7-10 days, marked by vulvar swelling and bloody discharge. Estrogen levels rise, but the bitch is not yet fertile.
2. Estrus – The fertile period, lasting 5-10 days, when LH surges and ovulation occurs. Progesterone begins to rise, and the bitch becomes receptive.
3. Diestrus – The post-ovulation phase, where pregnancy or a false pregnancy occurs.
4. Anestrus – The resting phase before the next cycle.

The most important event for breeders using frozen semen is the LH surge, which signals the beginning of ovulation.

What Is LH and Why Is It Important?
Luteinizing hormone (LH) is released by the pituitary gland and triggers ovulation. The LH surge happens suddenly and lasts only 24 hours, making it critical to test daily to catch this brief window.

Once the LH surge occurs:

• The bitch is fertile for only 24 hours.
• The eggs are released and ready for fertilization.
• The bitch is receptive and ready to mate.

Since frozen semen survives only 12-24 hours, insemination must occur at the precise moment the eggs are ready to maximize success.

How to Accurately Pinpoint the LH Surge

• Start Testing Early
  The LH surge typically occurs between days 7-12 of the heat cycle but varies among dogs.
  To ensure you don’t miss it, begin testing on day 5 or 6 of your bitch’s cycle.


• Perform Daily LH Tests
  Since the surge lasts only 24 hours, testing every day at the same time is essential. You can even test twice daily (morning and evening) to increase accuracy.


• Use Reliable LH Testing Methods
  
  Laboratory Blood Tests (the ideal)
  Conducted by a veterinary lab with quantitative LH analysis to provide precise values.
  Requires daily blood draws until the surge is detected.
  
  In-House LH Test Kits (Rapid Testing) Used by breeders or veterinarians to detect LH.
  Requires daily testing to track changes.
  Less accurate than lab tests but more convenient.


• Confirm the LH Surge with Progesterone Testing
  Progesterone levels begin rising slightly at the time of the LH surge.
  To double-check LH surge timing, use progesterone testing:
  Before LH surge: Progesterone remains low (<1 ng/mL).
  At LH surge: Progesterone starts to rise (1.5-2.5 ng/mL).
  After LH surge: Progesterone climbs rapidly (≥5 ng/mL within a few days).
  Note: if LH testing is unavailable, frequent progesterone testing (every 2 days) can be an alternative.


• Look for LH Surge Confirmation Trends
  To ensure you have correctly identified the LH surge, check for the following:
  ✓ LH levels rise suddenly, then drop the next day.
  ✓ Progesterone starts increasing from baseline (~2 ng/mL).
  Note: ovulation occurs ~48 hours after the LH surge and eggs mature 4-5 days postsurge, which is an ideal time for a frozen semen AI.

Why Is LH Testing Crucial for Frozen Semen?
Unlike fresh or chilled semen, which can survive in the reproductive tract for several days, frozen semen has a much shorter lifespan (12-24 hours after insemination). So timing must be precise - insemination should happen exactly when the eggs are mature. Miscalculating ovulation can result in fertilization failure and LH testing provides the most accurate prediction of ovulation, ensuring frozen semen is used at the right moment.

LH Testing vs. Progesterone Testing: Which Is Better?
While progesterone testing is helpful, it only estimates ovulation based on hormonal trends. LH testing is the only way to pinpoint ovulation precisely.

How to Plan Insemination After LH Surge Detection
Once you have detected the LH surge:

Best Methods for Frozen Semen Insemination Since frozen semen has reduced motility and lifespan, direct intrauterine placement is required:

Final Tips for Success

• Work with an experienced reproductive veterinarian familiar with LH testing and AI.
• Use a reliable LH test kit or veterinary laboratory to ensure accurate results.
• Store, handle, and thaw frozen semen properly to maintain viability.
• Combine LH and progesterone testing for the best accuracy.
• Use intrauterine insemination (TCI or surgical AI) for higher success rates.