Euthanized Gila cattle DNA could inform genetic selection in domestic cattle herds thanks to work by MU’s Decker
Dr. Jared Decker combines quantitative genetics – the realm that includes calculating EPDs – and population genetics – understanding the history of cattle populations, how different populations are interrelated, and how natural selection has occurred within those populations.
“I have a big interest in trying to better understand how cattle were domesticated,” he said. “What genes and what traits were under selection when we domesticated cattle approximately 10,000 years ago.”
Decker said if selection during domestication was on a complex trait, like docility or immunity, then those same genes under selection when cattle went from a wild environment to a human-controlled environment, those same genes would be under selection as cattle move from a domesticated environment to a wild environment.
To this end, his group collects and studies DNA samples from feral cattle populations across the world.
Decker, who is a Wurdack Chair of Animal Genomics, Associate Professor at the University of Missouri, grew up in northwest New Mexico and was already familiar with the wild cattle in the Gila Wilderness. When he learned the USFS was, in cooperation with USDA APHIS, euthanizing the cattle that were once under human management, he was anxious to collect DNA samples. Though he was unable to collect samples when cattle were shot in 2022, DNA samples from some of the cattle from the most recent removal are currently in transit to his team.
There are few wild or feral cattle herds in the U.S. On the remote island in southwest Alaska, Chirikof Island is home to one of those herds. Decker was able to, with the help of the USDA, collect and analyze DNA from 10 head of those cattle. Chirikof Island is about 29,000 acres and is 11 miles by 7.5 miles wide. He said there are a few feral herds in the UK, one in Hong Kong, and a herd of Dexter cattle that have become feral in South Africa.
Decker said when cattle are managed, there are a number of ways to alleviate various forms of environmental stress, be it disease pressure, parasite pressure, temperature, or various other stressors.
“When cattle are feral and are no longer being managed, they are much more at the mercy of natural selection and those environmental stressors,” he said. “In addition to better understanding the ancient history of domestication, these feral populations can also help us understand adaptation to challenging environments.”
Decker’s work on the Chirikof Island cattle published in a peer-reviewed journal was able to demonstrate the cattle are mostly a mixture of Russian Yakut cattle and the DNA patterns suggest the Russian cattle first arrived to the island, followed by U.S. breeds – primarily Hereford – appear once Alaska came under the control of the U.S. From the DNA patterns, it appears the mixture occurred about 120 to 60 years ago.
Although the sample size was small, Decker also analyzed signatures of selection revealed by the DNA samples. He said selection for genes related to cancer, immune-defense response, and embryonic development.
Not unlike the cattle in the Gila Wilderness that have been removed under the guise of being unauthorized and contributing to overgrazing and damage to riparian areas, the Chirikof Island cattle are facing a similar fate. According to Decker’s 2016 peer-reviewed article titled Origins of cattle on Chirikof Island, Alaska, elucidated from genome-wide SNP genotypes, the island became part of the Alaska Maritime Wildlife Refuge. In the 1980s, the US Fish and Wildlife Service began removing introduced species from various islands in the refuge, mainly foxes introduced by fur traders, but also cattle, although not from the isolated Chirikof Island at that time. Though grazing leases were granted in the twentieth century, the last lease expired in 2000 and permits to remove the cattle expired in 2003 with cattle remaining on the island today.
In 2013, the US Fish and Wildlife Service restated its intent ‘to restore these islands and finally help them fulfill their congressionally mandated destiny as a wildlife refuge’. As part of this destiny, federal wildlife managers seek to remove the cattle from Chirikof Island to stop grazing and enhance habitat for birds, likely resulting in the extirpation of the feral cattle. In the paper, Decker said “knowledge of the extent and nature of genetic diversity may aid in objective and rational decision making relative to potential conservation of this germplasm.” Definitively quantifying the origins, admixture and divergence of the Chirikof Island cattle relative to more readily accessible domestic cattle, therefore, was the goal of Decker’s team.
Decker’s work may be financially important to cattle producers as the research can inform breeding decisions.
“Those feral cattle would point us to the docility and temperament genes we do not want,” he said.
Docility, he said, is complicated and not influenced by a single gene and also is influenced by management and environment. Research on feral cattle can also inform the genomics of metabolism to identify metabolic efficiency and feed intake; genomic prediction of economically important traits; genetic tools to improve fertility; and genotype of environmental interactions.
They are, he said, at the beginning of a long process analyzing DNA samples from the Gila cattle. He was unable to secure samples from any of the Gila cattle that have been gathered and sold and said that is one sample that, if available, he would like to collect.
“There’s been about 60 years of selection and 12 generations of selection in the Gila cattle so it’ll be interesting to see how they’ve changed,” he said. “I know there’s been some concern about strays intermingled with the cattle. Those strays, though, are likely the ones most resistant to human control and management so it’ll be interesting to see what we find.”