Experts use rapid cooling to preserve bovine eggs

A Canadian initiative to preserve rare livestock genetics is taking a closer look at the germplasm of the bull’s better half.

The effort may help develop an improved protocol for preserving bovine eggs for posterity.

Genetic preservation in cattle has focused on male genetics, said Muhammad Anzar, a cryobiologist with the Canadian Animal Genetic Resources Program in Saskatoon.

“Semen technology is pretty much established,” said Anzar.

“But female genetics conservation is quite a bit (more) challenging.”

The topic is of particular relevance to researchers at the genetic resources program, who have worked for the last decade to preserve genetics of rare breeds no longer used in mainstream livestock production.

“If, God forbid, all the females are dead and we have the semen, but we don’t have oocytes (eggs), then we are in trouble,” he said.

Genetic material is often stored using cryopreservation, which uses liquid nitrogen and a slow freezing process. However, bovine eggs are more sensitive to ice crystals during freezing, which makes them difficult to preserve in this fashion, he said.

An alternative process, called vitrification, uses rapid cooling to preserve materials by keeping them in a “glass-like” state. This method has also proven problematic.

“With the semen, there is a 50 percent survival rate, with the embryos there are about 30 to 50 percent survival rate, whereas in the oocyte it is only 10 percent, using the vitrification technique,” said Anzar.

Researchers were able to use synchrotron technology at the University of Saskatchewan to take a closer look at the structure of the frozen egg. They found that ice crystals were still forming inside the egg, preventing proper preservation.

Further work is needed to better understand why that’s the case, but Anzar said vitrification will remain an important technique for genetic preservation because of its simplicity.

“It does not need a sophisticated computer … vitrification can be done in a simple mug of Tim Hortons,” he said. “You put the oocyte or embryo on that plastic strip and dip it into the liquid nitrogen directly. It can be done at a farmer’s doorstep to conserve the female genetics.”

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