Solution in sight for frozen pig embryo riddle

A small Australian research team believes it is poised to solve a 25-year-old riddle and open new horizons for the global pig industry.

The team, at the University of Queensland, says it is on the verge of developing the first commercially-viable process for freezing pig embryos.

The work could usher in a new era of disease-free international transfer of genetic material between pig producers.

Pigs are prone to contagious infections which are capable of inflicting enormous damage in modern piggeries based on intensive production environment of modern piggeries.

Bringing in breeding stock is a risky business yet isolated herds need continuous injections of outside genetic material to avoid becoming closed systems.

The best way to minimise infection risks is by transferring genetic material in embryonic cells which are still surrounded by the zona pellucida, a natural barrier against disease agents.

Unfortunately for breeders and producers, unfrozen embryos can't be kept alive long enough to survive international transfers.

But successfully freezing pig embryos has turned out to be an elusive goal for scientists because of a quirk of nature.

Early stage pig cells have a much higher lipid (fat) content than horse, goat or sheep cells.

While effective freezing techniques have been developed for the latter, freezing pig cells turns the lipids toxic and poisons the embyronic cells.

Over the past five or six years, researchers at University of Queensland School of Vet Science have refined a process that circumvents the problem by reducing lipid content inside cells without breaching the zona.

They are now attaining commercially-viable pregnancy rates of 70 to 75 per cent and litter sizes of up to 11, says research consultant Ranald Cameron.

Cameron, who has been involved with pig embryo transfers for at least 15 years, credits research scientist Dr Luke Beebe with making a central contribution to the solution.

Cameron first tackled the problem about six years ago in conjunction with biotech BresaGen and help from an Australian Research Council (ARC) grant.

When the ARC grant ran out several years ago, Cameron was unable to interest Australian pig breeders in underwriting continued research.

Then the world's largest pig breeder, US company PIC, agreed to fund the program via its R&D arm Sygen in return for an option over an exclusive licence for the technique.

In the past two to three years the research team has made rapid progress thanks largely to Beebe.

The protocol first uses a chemical to make cell cytoskeletons more flexible, then centrifuges the embryo to spin lipids out to the periphery of cells without compromising the zona pellucida.

When frozen and thawed, the lipids remain external to the cells, reducing their toxic effects.

A final key step in developing a successful protocol has been the use of vitrification, an ultra-rapid freezing method, on the centrifuged embryos.

By fine-tuning the various steps, the team is at the stage of producing near-commercial grade results from frozen embryos.

In fact, pregnancy sucess rates and litter sizes are already at a commercially-viable stage for high value genetic stock, Cameron says.

UQ's commercialisation arm, Uniquest, is negotiating with Sygen for increased funding for a new three-year research period. Negotiations with other, unspecified companies are also underway, according to Andrew Cecil, a Uniquest manager for innovation and commercial development involved in the talks.

Researchers want to see a near doubling of annual funding to $250,000 from $150,000 and initial indications from Sygen are positive, according to Cameron.

The next milestone will be take the technique out of UQ labs and demonstrate that it can successfully collect, process and transplant embryos under typical commercial piggery conditions.

Following that, developers will press the Australian Quarantine and Inspection Service (AQIS) and the International Embryo Transfer Society to give the technique their stamp of approval.

That will require a major breeder to make a formal request for the process to be examined and the government investigation could take up to two years.