Step into the freezer: Everything you need to know about freezing semen in your stud dog
As a veterinarian focused on canine reproduction, I’ve found that many clients don’t fully understand the freezing process or lack realistic expectations for pregnancy success when breeding to frozen semen.
Whether you’re looking to freeze or considering breeding your female to frozen semen, you need the full picture of what’s involved
Freezing canine semen is often seen as an ideal way to preserve valuable genetics for the future. With proper handling, frozen semen can remain viable for roughly 10,000 years, providing breeders peace of mind by perpetuating the genetic contribution of a prized stud dog.
For decades, frozen semen has been touted as a way to tap into past genetics and safeguard against the unexpected reproductive loss of a promising young dog. Many breeders have faced tragic accidents or illnesses that cut short the lives of exemplary prospects before their prime. In such cases, having a bank of quality frozen semen can be a lifesaver.
For certain, semen freezing looks good on paper, and that’s what most of the semen banks would prefer you focus on when deciding to freeze and store.
However, in practice, frozen canine semen has a mixed reputation. As a veterinarian whose practice focuses on canine reproduction, I’ve found that many clients don’t fully understand the freezing process or lack realistic expectations for pregnancy success when breeding to frozen semen. More often—like, almost always—breeders are unaware of the costs, effort, and outcomes associated with this approach.
This article aims to explain the freezing process thoroughly and highlight the pros and cons, both immediately and in the long term.
What’s Involved in the Freezing Process?
“In contrast, pregnancy rates with frozen semen can vary widely but often hover around 40% to 50%, even with perfect timing and advanced insemination techniques.”
Contrary to popular belief, frozen semen isn’t just fresh semen kept cold. Semen is a living matrix of sperm and other supporting fluids, sometimes numbering in the billions in a single sample. Freezing directly would be fatal to the sperm, as ice crystals would form and rupture their DNA like a beer chilled too long in the ice box. Instead, the sperm are separated from their natural fluids and placed in a cryoprotectant solution that shields them from the inherent swelling and subsequent severe freezing damage. After acclimating, the sample is gradually cooled before being plunged into a bath of liquid nitrogen at roughly -290 degrees Fahrenheit, a temperature that halts nearly all metabolic processes.
This deep freezing allows the semen to be stored more or less indefinitely, with minimal degradation in large vacuum-walled metal tanks (think Yeti tumblers in both function and price tag). These vessels can also be transported globally, making frozen semen a preferred choice for international shipping where there may be days to weeks of delay in transit or customs.
When it’s time to inseminate, the semen is thawed and brought to body temperature in a warm bath. The surviving sperm then resume their activity, ready to fertilize an egg, whether days or decades after being frozen. At least in theory, anyway…
Advanced (and often expensive) breeding techniques like this transcervical insemination are required for success using frozen semen. This fact is often overlooked by breeders who agree to store semen in their stud dogs.
The (Multiple, Unspoken) Downsides of Frozen Semen
My biggest concern as a reproductive veterinarian is that semen banks don’t often discuss the downsides of freezing.
First—and I’ll be blunt here—most frozen semen sucks. Even with precise timing and good motility, overall pregnancy rates and litter sizes with frozen semen are generally much lower than with fresh samples.
The process of freezing semen is harsh on the structural and genetic integrity of sperm, as one would expect with a polar plunge in liquid nitrogen. Sometimes the defects attributed to this process are obvious in a thawed sample, and other times the semen looks decent enough in our post-thaw evaluation but has less obvious damage to the cell membrane or DNA stored in the head, preventing fertilization of the egg. The freezing process itself can reduce sperm motility by half or more, and even the best samples only offer about 12 hours of viability once thawed, compared to nearly a week in fresh samples.
While frozen semen is a valuable tool for preserving genetics, it's important to note that pregnancy rates are generally much lower with frozen semen compared to fresh samples. Fresh semen, under optimal conditions, typically results in pregnancy rates of 80% or higher. In contrast, pregnancy rates with frozen semen can vary widely but often hover around 40% to 50%, even with perfect timing and advanced insemination techniques.
This limited viability and poor motility means that timing is crucial. Ovulation timing through progesterone testing is essential, and advanced insemination techniques, such as transcervical or surgical insemination, are required. Your turkey baster AI technique is simply not going to work here, so don’t waste money or time attempting it. These procedures and blood tests, along with the expense of long-term storage of frozen semen, can easily cost over $2,000. This hefty price tag is generally not discussed when a semen bank takes your money to store, presumably for fear of steering your business away when faced with the full financial picture.
Not all frozen semen is the same, either. I’ve enjoyed near perfect success with a bygone stud’s frozen samples, only to be humbled by multiple failures in a similar sample from the same breed. Sometimes, this variation in success has an obvious cause, and it often boils down to post-thaw motility and breeding dose. Far too often, there’s a discrepancy between the motility assessments provided by semen banks and the actual quality of the sample once thawed. Not every bank freezes the same way or provides a detailed assessment of their initial post-thaw quality, and your mileage here will certainly vary. It’s not uncommon for a shipment to have much, much lower motility than advertised, leading to disappointment when a garbage sample you’ve purchased from a breeder or paid to store for years is thawed on breeding day. No one likes to hear they’re faced with spending a couple grand for what will likely be a Hail Mary when they entered this process expecting a grand slam.
Generally speaking, banks also appear to lack a set standard for what constitutes a minimum breeding dose, or the minimum number of living sperm that are built correctly and generally swimming in a reasonably straight line. You may feel flush with 10 straws of stored semen on your long-gone stud, only to find out later the entire lot is good for about one (or maybe two) lean breedings when thawed. The paperwork that accompanies your semen often fluffs the post-thaw numbers, and it’s not uncommon for us to receive all the semen available for a stud and not have enough viable sperm in the sample to get the job done. No one is happy in this scenario, your repro vet included.
Strategies for Success
The adage “freeze early, freeze often” holds true. The best frozen samples come from young, healthy dogs with good libido and excellent semen quality in their prime fertile years (2-5 years old). Breeders should begin collecting from promising dogs early and maintain a diverse inventory of samples, ideally stored in different locations for safety. Stud dogs should be trained to collect (with an in-heat female present initially, so they learn to enjoy the process), much in the same way they’re trained to perform any other task asked of them at home or in the field.
Far too many breeders ask me to begin the process of freezing semen in an older male that is wholly unfamiliar with the collection process. Some of them have enjoyed long reproductive careers with natural mating and may be resentful of my intervention in the process. Timid or unsocialized males may never collect if not introduced to the procedure early in life and in a positive way.
Frozen semen should not be utilized merely for convenience. Far too many breeders who are inexperienced with frozen semen request this service so they can ship the sample early “for when the female is ready.” While I understand the motivation, particularly when the ovulation and breeding windows will likely fall during hunting, trialing or show season, the significant hit in fertility and pregnancy rates effectively wipes out any perceived benefit to this short-sighted strategy. If fresh chilled is available, do everything in your power to facilitate that type of breeding. Your likelihood of achieving a pregnancy or a decent litter size are exponentially higher in nearly every circumstance.
That said, if you feel you have several good samples stored, by all means don’t hesitate to use them while the male is still producing quality semen. I’m more enthusiastic about using frozen semen when a portion of the sample has been proven to produce healthy, live puppies. Periodically using a few breeding doses on young, fertile females can confirm the potency of stored semen and further justifies your expense in paying to store it.
“What is a Transcervical Insemination? A TCI bypasses the cervix and manually deposits semen directly into the uterus. The procedure requires no anesthesia and is associated with higher pregnancy rates in fresh and frozen semen.”
To further increase your chance of success, seek out the services of a reproductive veterinarian who has extensive experience with breeding with frozen semen. As I’ve previously mentioned, there’s a brief window of fertility using frozen samples, so hitting the nail on the head ovulatory speaking is essential. Find a vet that offers a transcervical or surgical breeding and is well versed in performing that procedure late in the fertile window when all the available eggs are ready for fertilization.
Diversifying your semen collections also safeguards against potential loss or damage to stored samples. While frozen semen can last thousands of years, practical considerations like tank failures or natural disasters can lead to untimely thawing and seem to follow a two-decade cycle. If a sample hasn’t been used in 20 years, it might not be worth storing any longer. Nostalgia alone doesn’t justify the expense.
Most importantly, breeders should approach frozen semen as a strategic tool rather than a last resort. If a frozen semen breeding produces a male pup that embodies all the desirable traits of his sire, let his fresh semen (and not an older bank of frozen semen) become the new cornerstone of your breeding program. He can carry those valuable genetics forward more efficiently than dipping into frozen semen at every breeding.
In my view, there’s far too much nostalgia attached to frozen semen. While it’s tempting to rely on the genetics of a past stud dog, a strong breeding program should focus on creating better representatives of the breed for the future. If you find yourself frequently returning to old genetics, it might be a sign that your breeding goals aren’t being met.
