The relatively new technology allowed this Canadian purebred herd to protect its top blood-lines while ridding it of the PRRS virus.

Embryo transfer technology has transformed Arnold Ypma's herd of 280 purebred Duroc sows from an all-PRRS-positive (porcine reproductive and respiratory syndrome) herd to an all-negative status.

Ypma's herd, Shade Oak Swine near Culloden, Ontario, is probably the first embryo-transfer herd in North America. Because the technology worked so well, it likely will not be the last.

A husband-wife team of veterinarians, John Pollard and Marie-Claire Plante of Ontario Veterinary College, developed the technology and ran trials demonstrating that the PRRS cycle could be broken. Their application of the technology in Ypma's herd proved it works in the field as well as it did in the college's research facilities.

Ypma's aim was to rid his herd of PRRS and a few other diseases without disrupting his genetic selection program. He's delighted to report his barn is filled again with 280 top-notch Duroc sows from his best bloodlines.

Cleanup, Selection Programs Ypma began by totally vacating his barn in May 1999. He thoroughly washed the barn, disinfected it twice, then left it sit idle for two months. There wasn't a pig on the place.

Sixty of his best sows and gilts were selected and moved to rented facilities. Those sows and gilts - the top 10% selected from each genetic line to maintain genetic diversity - became embryo donors. Selection criteria focused on average daily gain, feed conversion and lean meat yield.

The embryo recipient sows were crossbreds purchased from Pureline Swine of Guelph, Ontario. The Pureline herd was chosen because of its high health status.

The donor and recipient sows were treated to synchronize their estrous periods in groups. Embryo transfers were completed in eight batches over a nine-month period. The sows and gilts for those batches were chosen from performance trials that continued at the rented facilities.

By continuing his performance-testing program throughout the process, Ypma maintained full genetic selection pressure and progress. "We didn't feel we could afford to lose a year," he says.

All of the donor sows have gone to slaughter. The crossbred recipient sows were culled as Ypma needed space for the purebred Durocs from the embryo-transfer litters. All replacements were performance tested to ensure the best genetics would serve in the next generation of Shade Oak genetics.

Litter Size Litters from recipient sows were smaller than Ypma anticipated, averaging about 8 pigs/litter - about three short of his normal litter size average. Litter size ranged from three to 11 pigs.

Still, Ypma believes the technology worked well enough to get a good cross-section of Shade Oak's best genetics. He took single litters from most females, but he got three litters from his most valuable sow.

Ypma had used Caesarean section as a disease-eliminating technology since he began farming on his own in 1985. However, in this case, he decided to spend more for embryo transfer technology in order to eliminate PRRS. "It's possible for PRRS to cross the placenta during early pregnancy," he explains, therefore Caesarean-section procedures likely would not have eliminated the virus.

"That's not to say that we can stay free of PRRS forever," he acknowledges. "But, we felt it was important to try to get as clean as possible." So far, all of his pigs are testing negative for PRRS.

Costs Pollard charges $700 (Canadian), roughly $460 (U.S.), per donor sow for the procedure. The embryos collected/donor are enough to transfer to 1.7 sows on average, he explains. Then there's a $500 cost/recipient sow ($329 U.S.). The husband-wife embryo transfer team runs a business called Therion and can be reached at (519) 763-2085.