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When artificial breeding is better than natural: the case of the wood bison

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Bison are of two main types: plains and wood. Almost hunted to extinction, the wood bison in particular were registered as "threatened" in the 1960s, and were bred back to plains bison to increase their numbers. Unfortunately, the sperm of these breeding animals also carried serious diseases – deadly tuberculosis and endemic brucellosis (which can cause miscarriages) – that can be transmitted to humans.

Using assisted reproductive technologies like cryopreservation, artificial insemination, and embryo transfer, Agriculture and Agri-Food Canada (AAFC) scientists and their counterparts at the Western College of Veterinary Medicine (WCVM) in Saskatoon are helping both the bison population and the industry itself.

Dr. Gregg Adams, of WCVM, has devised a way to "wash" these pathogens from embryos using enzymes. Once washed, embryos will no longer carry the diseases, which will result in the regeneration of a larger, healthier population of wood bison more quickly through embryo transfer. This kind of genetic conservation is not something that could be efficiently done by nature alone.

In turn, AAFC scientist Dr. Muhammad Anzar has developed a technique to improve wood bison genetics: a "clean" way to freeze semen.

Semen freezing is a common approach to conserve the male genetics for use in artificial insemination and embryo transfer. Conventionally, semen is frozen in a medium containing either egg yolk or milk. However, both animal protein sources can have biosecurity risks. Because of this, the risk of disease transmission is a main limiting factor in the exchange of bison genetics, as countries looking to improve their herd’s genetics do not want to import these potential biosecurity hazards.

Dr. Anzar’s lab developed a clean technique in which the egg yolk or milk component has been totally excluded from the medium used for semen freezing, which makes the sharing of diverse wood bison genetic material easier. Although currently only being applied for the conservation of bison and bull semen, this new technique has the potential to be applied elsewhere, thus improving the international exchange of genetic material across numerous fields.

"At this moment, pathogen-free conservation of wood bison genetics is the most crucial issue in bringing the number of wood bison up. The successful conservation of the bison species and exchange of germplasm within and between countries will ultimately benefit the growing bison industry."

- Dr. Muhammad Anzar, Research Scientist (Cryobiology), Agriculture and Agri-Food Canada

Improvements in the genetics of wood bison will continue, thanks to the ongoing work of this AAFC-WCVM partnership, the Ministry of Agriculture (Government of Saskatchewan), and the Saskatchewan Bison Association, as well as the willingness of private bison producers to continue their support.

Key discoveries

Photo gallery

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Dr. Anzar inspects straws of bison semen.
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Bison semen processed in a freezing medium without egg yolk (left) and with egg yolk (right).
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First bison calves born following artificial insemination with frozen semen.

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