A new study published in the journal Scientific reports revealed the strongest evidence to date that all North American bison carry several small, but clearly identifiable, DNA regions from domestic cattle.
In the study, Texas A&M University College of Veterinary Medicine & Biomedical Sciences (CVMBS) researchers, led by James Derr and Brian Davis, compared genome sequences among large historical bison pedigrees in 1,842 domestic cattle, finding that all analyzed bison genomes contained evidence. pet introduction.
“This comparative study clearly shows that the people responsible for saving bison from extinction in the late 1800s are also responsible for introducing bovine genetics to this species,” Derr said.
This study updates the results of a series of studies published 20 years ago in which Derr’s team found that there were only a few bison herds that appeared to be free of introgression of domestic cattle. Today, these researchers, thanks to better genetic technology, have shown that even these herds are not exempt from hybridization.
“Today, it appears that all major bison herds in public, private, tribal, and non-governmental organizations have low levels of bovine genomic introgression,” said Sam Stroupe, Ph.D. student in Derr’s laboratory and first author of the study. “This includes Yellowstone National Park, as well as Elk Island National Park in Canada, which was considered free of livestock intrusion based on previous genetic studies.”
Derr said these new findings will also have implications for bison conservation. in this case, their results could actually help with conservation efforts, as some herds no longer need to be isolated.
The legacy of crossing
This common genetic lineage is the result of multiple hybridization events between North American bison and cattle over the past 200 years, which followed the well-documented bison population decline of the 19th century.
These hybridization events were primarily man-made, as cattle farmers in the late 1800s deliberately bred domesticated cattle with bison in an attempt to create a better meat-producing animal. Although the crossover was successful, they did not reach their primary goal and the effort was largely abandoned.
At the same time, William Hornaday and the American Bison Society began national conservation efforts, sounding the alarm that North American bison were on the verge of extinction. As a result, a national movement began to establish new bison conservation populations and preserve existing bison populations.
The only bison available to establish these new herds were almost exclusively animals from the ranchers’ private herds.
“As a result, these well-meaning hybridization efforts leave a complicated genetic legacy,” Davis said. ‘Without these private herds, the bison could be extinct. At the same time, this deliberate introduction of DNA across species resulted in remnants of bovine footprints in the genomes of the entire contemporary species.
“We now have the computational and molecular tools to compare genomic bison sequences with thousands of cattle and finally determine the level and distribution of livestock genetics in bison representing each of these historical bison strains.” , he declared.
Derr says it is important to recognize that while hybridization between closely related animal species has occurred naturally over time – well-known examples include coyotes and eastern wolves, grizzly bears and bears, polar bears, as well as bobcats and Canadian lynx – bison-cattle hybridization is almost exclusively a deliberate, man-made event that coincided with the huge population bottleneck in the late 1800s.
“Two major events, an extremely small bison population and widespread interest in developing hybrid animals, have altered and shaped the genomes of this species in ways we are only just beginning to understand,” Derr said. “Yet this species survived and now thrives on the plains of North America.”
Feedback from the bison conservation community
As one of the world’s most iconic animals, bison play a number of important and sometimes conflicting roles in society.
While some consider them a wild species that should not be tamed, others regard them as an important economic livestock; Although bison are farmed as wild animals in state and federal parks and animal sanctuaries, most bison that live today are owned by private ranchers and farmed for meat and fiber production.
For others, they have religious and spiritual roles, just as they are icons of continental pride. In 2016, the bison was even named America’s National Mammal.
“Although seen in different ways, bison conservation is a priority for many different groups, and it is imperative that we agree to use the best available scientific information to make future decisions,” Stroupe said. “These results clearly demonstrate that by using modern genomic biotechnology, we can uncover many historical details regarding a species’ past histories and use this information to provide informed management when determining conservation policies for the future.”
Although many of these cattle herds are quite small with 100 animals or less, there are a few exceptions. Turner Enterprises in Bozeman, Montana, is the largest private bison producer with more than 45,000 animals spread across several states.
According to Mark Kossler, vice president of ranch operations, Turner Enterprises will use this new information to further improve its conservation efforts.
” Turner Enterprises has been using Texas A&M University’s genetic work for bison for the past 20 years to structure the genetic management of our maternal herds regarding the introgression of bovine mitochondrial DNA, ”he said. “We were fully aware that advanced technology and mapping of the entire bison genome could reveal that all bison core DNA could also have bovine introgression.
“Knowing that the North American bison herd exhibits widespread introgression of bovine DNA, albeit in small amounts, will enable our operations to structure future genetic management between our herds to maintain a broad genetic diversity without fear of cross-contamination from herds. , which was perceived as ‘Introgression-free’, he said. “This is useful information for the bison community. We value the research and diligence of Texas A&M University in providing the bison community with the ultimate answer to this question of the genetic purity of bison. »
Les Kroeger, president of the Canadian Bison Association, which helped fund Derr’s research, agreed that better information is always a positive step in their efforts for sustainability and conservation.
“As research tools improve, we get a better understanding of the complex history of bison,” he said. “With this information, we can continue to pave the way for the growth of healthy populations of this iconic animal for the benefit of future generations.” The commercial bison industry continues to support research and conservation initiatives, while continuing to produce high-quality protein in a sustainable way for the benefit of consumers. . »
Chad Kremer, president of the National Bison Association, added that this information will provide bison producers across the country with better information to manage their herds.
“The National Bison Association welcomes these research findings as we continue to unravel the long and complicated genetic history of American bison,” he said. “Research projects like this continue to help producers in their ability to maintain healthy and diverse genetics in bison herds today. Genetics is the cornerstone of modern herd management, and something the National Bison Association strongly promotes in its outreach and producer education. Across the continent through our North American bison registry. We hope that bison producers will use this data and technology to continue to improve the genetics of their own herds while continuing to restore bison to their native landscape.