Genetic research in wood bison may have wider implications for wildlife conservation and for the Canadian livestock industry. Scientists have developed tools using assisted reproductive technologies such as cryopreservation (freezing), artificial insemination (AI) and embryo transfer which could help increase dwindling wild bison populations and prevent the spread of disease.
Canadian wood bison is an indigenous species that is perilously close to losing too much of its genetic diversity to be able to survive for the long term. Past efforts to preserve the species included interbreeding them with Plains bison and domestic cattle, which produced hybrids that don’t contribute to build wild bison genetics. In addition, 30 to 60 per cent of the remaining wood bison population carries cattle diseases such as brucellosis and tuberculosis (TB).
A new preservation strategy
For the past 10 years, the Wood Bison Research Group which includes scientists at the University of Saskatchewan and Agriculture & Agri-Food Canada (AAFC) has been working to develop tools for producing and preserving clean, disease-free wood bison germplasm.
Gregg Adams of the Western College of Veterinary Medicine (WCVM) in Saskatoon is the principal investigator on the project and has recently been working on techniques to “wash” brucellosis pathogens from embryos and semen. Once washed, embryos and sperm no longer carry the disease, and therefore can be used to regenerate a healthy wood bison population quickly through embryo transfer and AI.
“We have produced over 400 wood bison embryos and have over 100 preserved in liquid nitrogen tanks. From initial studies, we now know that we can wash the semen, embryos and eggs free from brucellosis organisms,” says Adams.
“The summer of 2016 showed proof of concept was complete with the birth of three, live, healthy bison calves from the transfer of in vitro fertilized embryos and one from a frozen embryo.”
AAFC scientist Muhammad Anzar is a project lead on the development of frozen bison semen fit for AI. Semen is conventionally frozen in a medium containing either egg yolk or milk to protect the sperm cells against cold shock. However, there is a risk that disease pathogens can hitch a ride in these animal proteins added to the semen extender.
“The technique that I developed for the cryopreservation of semen is without adding egg yolk or milk in the semen extender,” says Anzar. “The advantage of this ‘clean’ semen is that it is as good as using egg yolk, which is a common extender, but it’s free from any external pathogens or micro-organisms.”
Benefits for the livestock industry
This new technique has the potential to be applied elsewhere.
“We have eliminated the possibility of disease transmission, so our research is very beneficial for the bison industry and it will also be well taken by the dairy and beef AI industry too,” says Anzar.
Many countries such as Japan and Europe have regulations that require any imported livestock semen and embryos to be free of pathogens. The risk of disease transmission is certainly the main limiting factor in the exchange of bison genetics worldwide, as countries looking to improve their herd’s genetics do not want to import these potential biosecurity hazards.
And the research could help wildlife conservation efforts come full circle and reverse a chain of infection that they helped cause in the first place. “Elk and bison are the two main wildlife reservoirs for brucellosis and TB in Canada and U.S.,” says Adams. “Elk are infected from bison and it’s from elk that there have been documented cases of transmission to cattle. This is a reasonable strategy to begin the clean up process, to improve the genetic diversity of the bison species and to prevent the possibility of infection of our healthy livestock with these diseases.”