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Any breeder will say frozen swine semen most commonly used for artificial insemination (AI) is finicky, with a useful life of only a few hours once it’s thawed. To make matters worse, sows generally only conceive when inseminated at particular times, leaving a very small window for successful conception.

That’s why University of Guelph Prof. Glen Cassar and graduate student Miguel Valcarce, Department of Population Medicine, are trying to find ways to make swine breeding more efficient. With a combination of impeccable AI timing and a new thawed semen preservation method, the researchers are developing a new strategy they hope will increase successful AI breeding rates in swine.

“These new methods have so far managed to save a lot of time, labour and money,” says Valcarce. “Suddenly, AI has become a much more efficient process.” Frozen semen allows for higher biosecurity standards in herds, unlimited preservation of top quality genetic lines and worldwide access to valuable animals, he says. Although AI with frozen semen is commonly used to breed many species, it isn’t very successful in swine. Freezing swine semen has been known to damage sperm cells – and once thawed, sperm cells only last four to six hours.

Now, after experimenting with different sperm stabilizers, Cassar and Valcarce have found that adding seminal plasma – the component of boar semen that contains proteins, sugars and lipids but no actual sperm – to thawed boar semen prolongs the fertilization ability of frozen sperm cells to at least 12 hours. The researchers are combining these findings with their ongoing research on AI timing for higher sow conception rates. With the exact timing required for AI breeding in swine, says Valcarce, those extra hours can significantly increase chances of successful insemination.

Another major challenge among swine breeders is pinpointing the exact timing of ovulation during an estrus cycle. With the short lifespan of thawed sperm cells, breeders using AI can only hope that they’re inseminating sows during the critical hours before ovulation, when conception is most likely to occur. A sow is generally in heat for three days in breeding season, during which time breeders may be inseminating them up to three times. That’s inefficient, unreliable and time-consuming, with many expensive semen samples going to waste. Adding another six to eight hours of life to thawed sperm increases the likelihood that sperm cells will be active during ovulation, boosting the rate of successful AI.

Research by Cassar has simplified the AI process even further, by clearing up the grey area between the onset of estrus and ovulation. While it’s known that three to five hours prior to ovulation is the optimal time for conception, producers had no way of determining when the sow was at that stage. So, Cassar used two synthetic hormones to control ovulation very precisely. This method, which is available to producers, optimizes swine AI and allows for higher pregnancy rates while using less boar semen.

Preliminary results are promising. Historically, swine AI breeding with frozen semen shows low pregnancy rates, says Valcarce, but so far he has found that conception rates become similar to those seen with fresh doses when timed AI is combined with their thawed sperm preservation technique. In the future, the researchers want to isolate the exact components in seminal plasma that are responsible for the preserving effect in thawed semen. They also hope to maintain high numbers of sows that reach full-term in their pregnancies.

University of Guelph Profs. Mary Buhr, Department of Animal and Poultry Science, and Robert Friendship, Department of Population Medicine, are working together in this research, which is being sponsored by Ontario Pork. For more information, contact Jean Howden, Ontario Pork research coordinator, at 1-877- 668-7675 or jean.howden@ontariopork. on.ca.

Source: Ontario Pork - June 2005

Judy Maus is a writer with SPARK, the University of Guelph’s student writing program.