Freezing Canine Semen in Pellets

What Is Pellet Freezing?

Pellet freezing is a method of cryopreserving (freezing for long-term storage) dog semen by dividing the semen‑extender mixture into small drops, freezing each drop into a pellet, and storing those pellets in cryovials in liquid nitrogen. Compared to straws, pellets are much smaller (often 25-50 µL per pellet), which allows for very rapid freezing of each unit. This helps protect sperm cells from damage during the freeze‑thaw cycle.

Why Choose Pellets?

Improved survival of sperm: Because each pellet is a very small volume, temperature changes during freezing happen quickly, reducing the risk of ice crystals inside sperm cells and helping maintain better motility after thawing.

Higher conception rates in some cases: Some reports show that when pellets are used, especially with intrauterine or surgical insemination and well‑timed ovulation (progesterone/LH monitoring), conception rates can be very high—sometimes above 90%.
More doses from one ejaculate: Because pellets are small, a single good‑quality ejaculate can be divided into many doses, giving breeders more flexibility.

Storage and handling convenience: Pellets occupy less space, are stored in screw‑cap vials, and multiple vials can be stored together in liquid nitrogen tanks. Thawing is done by vial (one or more pellets) so you thaw only what's needed.

What to Expect/Limitations

Pellets are more sensitive to protocol quality: timing, drop size, cooling rate, extender composition, and lab/hands‑on skill matter a lot. Errors in any step can reduce post‑thaw sperm quality.

Frozen (and especially pellet‑frozen) semen has shorter lifespan after insemination than fresh or chilled semen. It often needs to be deposited as close to the site of fertilization (intrauterine by transcervical or surgical insemination) and at the optimal time in the bitch’s cycle. Vaginal insemination with frozen semen usually yields much lower pregnancy rates.

There may be wide individual variation in fertility: even with good post‑thaw motility, some sires perform much better than others in achieving pregnancies.

Our Process (What We Do)

Collection & Pre‑Freeze Evaluation
- Appointment to collect semen via manual collection. No sedation required. Behavioral conditioning, when needed, is addressed.
- Immediate evaluation of the ejaculate: volume, sperm concentration, motility, morphology.
Extension & Cooling Down
- The semen is diluted in a specialized extender that includes buffers, sugars for energy, cryoprotectant agents (like glycerol), membrane protectants (egg yolk or lecithin), and antibiotics to prevent bacterial growth.
- Two‑step dilution: initial dilution at room temperature; chilling to ~4‑5 °C; then final dilution just before freezing with the cryoprotectant. This gives the sperm time to adjust to the cold.
Pellet Formation & Freezing
- Small drops (25-50 µL) are placed into depressions (on dry ice or a cooled plate) so they freeze quickly into pellets.
- The pellets are transferred into labeled cryovials as soon as they freeze. The vials are then plunged into liquid nitrogen (or vapor phase as appropriate) and stored at ~ ‑196 °C.
Quality Control / Post‑Thaw Testing
- One pellet is thawed to test post‑thaw motility and viability. This helps us verify how well the freezing process worked for that ejaculate.
- Based on post‑thaw findings, we determine how many pellets will be considered one insemination dose for that male.
Storage & Labeling
- Each vial is labeled clearly with donor dog, date, batch, and in locking screwtop cryogenic vials.
- We store in secure cryotanks with daily checks for nitrogen levels and temperature stability.
Thawing & Insemination Advice
- Thawing follows a strict protocol: often in a warm water bath (temperature and duration matched to how the pellet was frozen).
- For best success, we recommend intrauterine or transcervical insemination, timed carefully according to ovulation (using progesterone or LH surge monitoring).

What’s needed from you(owner/breeder)?

Bring your male dog in good health.

Accurate timing of the female’s estrus cycle is essential. Progesterone or LH testing is often necessary.

Be prepared for using advanced insemination techniques (transcervical or surgical) for frozen pellets, rather than simple vaginal insemination, for best conception rates.

Success Rates & What You Might Expect

With well‑performed pellet freezing, properly timed insemination into the uterus (or via surgical means), conception rates can reach 90%+ in some cases.

More commonly, pregnancy rates with frozen semen are lower than fresh: several studies report ~60‑70% conception using frozen semen (under ideal conditions) vs ~80‑85% or more with fresh.

The number of pups in a litter tends to be similar to what you’d expect with fresh semen if everything is done well.

However, some sires have much better fertility than others after freezing. Even with similar motility post‑thaw, two male dogs may differ greatly in their actual pregnancy/whelping rates.

What You Should Know

Pellets work best with high-quality semen. Not all dogs freeze equally well, and some may require more pellets per breeding.

Precise timing is key. Frozen semen has a short window for fertilization, so insemination needs to be done at the right time — usually with progesterone testing and intrauterine (or surgical) insemination.

It’s an investment in your dog’s legacy. Whether your stud is active now or you're planning ahead, pellet freezing gives you options for future litters, even years down the line.

Frequently Asked Questions

How long does frozen semen last?
Indefinitely! As long as it’s stored properly in liquid nitrogen, it can be used years or even decades later.

How many breedings can I get from one collection?
It depends on your dog’s semen quality, but we often get multiple breeding doses from a single ejaculate.

Can you ship the frozen semen?
Yes! We can ship the pellets in special liquid nitrogen containers designed for safe transport.

What does insemination with pellets involve?
It typically requires precise timing and placement into the uterus using a specialized technique, often guided by hormone testing.

Ready to Get Started?

Whether you’re preserving your stud’s legacy, preparing for future breedings, or planning to ship internationally, pellet freezing is a smart, reliable option.

Spermbot by Spermtech –
Smarter Semen Handling for Healthier Litters

High-Tech Help for Breeding
The Spermbot is a smart machine that evaluates and helps freeze canine semen with great care and precision.
Keeps Sperm Strong
It protects semen, so it stays healthy and active, even during freezing and shipping.
Fast & Accurate Testing
Spermbot checks the quality of the semen quickly looking at how many sperm are there, how well they move, and if they look normal.
Clean & Safe Process
The robot works in a clean, sealed system, which means less chance of contamination or human error.
Great for Long-Term Storage
Spermbot is perfect for freezing and storing semen for months—or even years—without losing quality.
No Waste, Just Results
It uses just the right amount of semen needed, so nothing goes to waste.
Better Breeding Choices
With accurate semen info, breeders can make smarter decisions and improve litter health.
Everything Is Tracked
Every step is recorded, so you know exactly how your dog's semen was handled and stored.
Trusted by Vets
Many top vets and breeding professionals trust Spermbot for its safety and reliability.
Future-Ready Breeding
With advanced tools like Spermbot, your breeding program is set up for long-term success.

While we're experts in semen collection, storage, and handling, we’re NOT veterinarians. For any health or medical questions about your dog, please reach out to your veterinarian—they’re the best source for advice and care.