Colorado State University team strives to find genetics associated with grazing behavior
Milt Thomas, Colorado State University (CSU) professor and Rouse chair, says cattle from CSU’s Rouse Ranch are asked to perform in a variety of ways, and the operation must produce livestock that can successfully graze in the valleys of southeast Wyoming but also on the high-mountain slopes.
“As we start up these slopes, it takes a much different critter to get out there and forage in rough rangelands,” Thomas says.
CSU began looking at and tracking cattle performance on rangelands, eventually asking the question, “How much of that is genetic?” he continues.
Further, Thomas says data show that improved grazing distribution comes through use of products like protein lick tubs or other minerals. Using these products, he continues, is easy in lower-elevation pastures or even mountain areas with road access, but Thomas notes, in wilderness areas, distributing supplements, adding fences or improving water to change grazing distribution isn’t always an option.
“It might be two dollars a linear foot to build fence in good country, but that jumps to five dollars in rough country sometimes,” he says. “The next thing we know, we’ve spent more money on infrastructure than the entire ranch is worth.”
Thomas notes, “Then, we got into the idea of whether we can select cattle based on genetics that distribute across the rangeland. Therefore, we get cattle that just work and distribute across the range, rather than us having to herd them.”
As CSU’s research team traveled the world collecting data, Thomas says, “Some cows are bottom dwellers, while some were hill climbers. That’s just where they prefer to graze.”
Utilizing GPS data collected over the course of their study, Thomas and New Mexico State University’s Derek Bailey developed two indexes – the Rough Index and the Rolling Index.
The Rough Index incorporated slope and elevation, while the Rolling Index included both slope and elevation, as well as distance from water.
Cows were classified phenotypically as bottom dwellers, average or hill climbers using GPS data.
“We got 80 cows phenotyped and genotyped,” Thomas explains, noting that the gene was very polygenic, showing many genes that were associated with the trait for both indexes. “There is no one single gene that drives how or why a cow goes out and does this, but there are high points.”
In looking closer, the research team began looking for specific genes which might be particularly important, locating a handful of key contributors.
“Derek started talking about GRN5, the glutamate receptor metabolic form number five expressed in a part of the brain that controls appetite,” Thomas explains. “That gene is known for being involved in locomotion, motivation and special memory. That’s one of many genes that is important and probably has something to do why some cows will go further and why some cows will climb higher.”
However, for that particular gene, Thomas expressed it isn’t possible to tell whether the cow is actually hungry and seeking food or satiated, full and “just wants to go on a hike,” he comments.
“Now, we can start using these technologies to start to exploit grazing distribution,” Thomas says.
After their initial study, CSU obtained funding from the Western Sustainable Agriculture Research and Education (SARE) program to continue their research through a multi-disciplinary approach.
“Derek and his team at New Mexico State are range science folks, and they are in charge of tracking cows and working with phenotype data,” explains Thomas. “Our group at CSU is working on the genetic side of it.”
The team hopes to develop a breeding value from the data collected, in collaboration with teams from University of California, Davis and University of Arizona.
“In our second study, our goal is to get 400 cows both phenotyped and genotyped,” Thomas comments. “We will keep tracking cows as long as we have money to send collars. Our goal is to get cows tracked in every western state.”
The team sent groups of 20 collars to ranches across the West and is working to build their database of animals with both phenotype and genotype.
“We took the five initial genes, which included GNR5, and started doing SNP discovery,” explains Thomas, noting that SNPs are regions on the genes that are significant. “We went to those genes and looked them to see whether we find a lot of markers on the gene that might tell us more about the function of the gene.”
The team found 1,090 markets in Angus cattle, 560 in Brangus and 376 that overlapped between the two. Compared to their reference inbred Hereford female, the researchers found 10 overlapping markers across the three breeds that may provide useful tools for segregating cattle based on whether they are “hill toppers or bottom movers,” says Thomas.
Analysis and validation
Analysis continues to use more powerful statistics that have less error and more power in looking at distribution.
“There are some real challenges in that we have many, many more markers than we do phenotypes,” Thomas explains. “That is a real problem. We’ve had to do interesting things to validate markers.”
With initial evaluation of several markers, including a marker on chromosome 15, Thomas says, “With analysis, markers have validated, but it’s a challenge that we need more data to really work with the analysis that we’re doing today.”
Ultimately, Thomas says the research team hopes to develop a breeding value by coupling genotypic and phenotypic information.
“There is no doubt the genetics of grazing distribution is a complex trait,” Thomas summarizes. “I predict we’ll probably do research with the data set we’re developing over the rest of our careers.”
Despite the complexity of the work, Thomas says some markers have been found, but the trait is highly polygenic.
“There’s not one single magic gene or magic marker that tells us why a cow walks up the hill or stays at the bottom,” Thomas comments. “There is a lot of work we have to do to translate this to the industry, but we’ve got to start on it.”
Thomas spoke during the 2018 Beef Improvement Federation Conference, held in mid-June 2018 in Loveland, Colo.
Saige Albert is managing editor of the Wyoming Livestock Roundup and can be reached at firstname.lastname@example.org.