Freezing boar semen extends the life of that semen, allowing it to be stored for long periods of time and transported over long distances. However, there are obstacles to widespread use of this technology.
The biggest stumbling block is frozen semen’s decreased reproductive efficiency. You can expect farrowing rates to fall by about 10 percent to 20 percent with frozen semen, and litter size can be 1.5 pigs smaller, says Billy Flowers, reproductive specialist, North Carolina State University.
However, if individual boars are selected based on their sperm’s ability to survive the freeze/thaw process, and insemination occurs within a few hours of ovulation, sow reproductive performance can be equal to that of fresh semen says Brad Belstra, IMV International.
“A swine genetics company in Europe routinely achieves farrowing rates greater than 85 percent, and litters of 12 pigs born alive using frozen/thawed semen,” he notes. “Extra attention must be given to semen handling, heat detection and insemination timing to be successful with frozen semen.”
Costs are another obstacle to frozen semen use in the United States.
“Using frozen semen wouldn’t be economical for terminal market hogs or F1-Yorkshire or F1-Landrace animals,” says Harold Hodson, president Swine Genetics International. “You have to start with more semen because you lose 40 percent of the dose when you freeze it.”
Labor and equipment costs are higher to process the frozen semen. Semen freezing costs range from $6 to $12 per dose, which is higher than the selling price of fresh semen for terminal genetics in many cases, says Hodson.
“The freeze/thaw process is certainly more technical and requires more costly equipment than handling and storing fresh semen,” says Belstra. “A cost difference is difficult to calculate because it depends on the specific methods used and whether or not you include the frozen semen’s potential biosecurity and genetic benefits.”
As noted earlier, not every boar’s semen freezes well. Hodson says about 90 percent of boars that have good quality semen have no problems with it freezing. But again, variability is high. Belstra notes that it’s not uncommon for 30 percent to 60 percent of boars with good fresh semen quality to be rejected because they produce unacceptable results when it’s frozen and thawed.
Given these reasons, frozen semen isn’t expected to take U.S. pork production by storm any time soon.
Of course there are some advantages, and frozen semen can be used effectively in certain situations.
“Frozen semen has a much longer shelf-life than fresh semen,” says Flowers. “Fresh semen has a shelf-life of about 48 hours to 72 hours with a short-life extender. Different extenders could increase this time. Frozen semen would allow producers to buy all of their boar semen at one time and use it as needed.”
This sort of on-demand supply could be particularly useful to breed gilts, which have a more unpredictable estrus than weaned sows. Another advantage to frozen semen is that it could be used at the end of a breeding week to eliminate the costs of
ordering and shipping additional semen doses.
The extended shelf-life makes frozen semen ideal for exports — which is now the biggest user of the technology. The cost of shipping fresh or frozen boar semen overseas is about a wash, says Hodson. Certainly, the efficiency gap between fresh and frozen semen narrows when shipped overseas.
There also are some opportunities for specialized use in the United States. For example, USDA has a program in place to preserve swine genetic resources by freezing and storing boar semen.
“Producers also could store frozen semen for insurance,” says Olivier Coutre, IMV International. “It can be part of a contingency plan for porcine reproductive and respiratory syndrome or other diseases.” That’s because in the event of a disease outbreak requiring herd depopulation, or some other natural disaster, frozen boar semen could be used to restore lost populations, points out Belstra.
Some countries only allow frozen semen to be used following blood tests for certain disease conducted prior to and after its freezing.
Of course, because of the genetic variety and extended access, frozen semen has a niche in the show pig area.
Right now only a handful of companies offer frozen boar semen, and it really isn’t practical for commercial use. However, technological advances may make it more user-friendly, economical and feasible for commercial use in the future. In the end, it can provide a bit of an insurance policy.