Taking the genetics of grazing distribution literally to the next level
By Jaime Pullman
Every wonder why some cattle don’t mind making the hike up the hill for the fresh grass, while others would rather root around in the dirt at the bottom? Lucky for us, some researchers from several universities did, and decided to find out why. Turns out, there is a pretty significant genetic influence for grazing distribution.
Derek Bailey is a professor from the Department of Animal and Range Sciences at New Mexico State University, but before he joined academia, he worked as a consultant helping to resolve range management disputes between ranchers and the government.
“I monitored a lot of rangeland in the Great Basin,” says Bailey, “and I noticed that, typically, the biggest issue wasn’t the number of cows on a given piece of land, but their distribution.”
Fast-forward a few years and Bailey is now a part of a multi-university collaboration of researchers from New Mexico State University, University of California-Davis, Colorado State University, and University of Arizona that have found genetic markers for grazing distribution.
Breeding cows with an interest in climbing has significant ecological and economic benefits. Cows have a tendency in large pastures to hang out and overgraze particular areas, often riparian. But if more cows are willing to walk up the hill, those areas can be better protected. From a sustainable rangeland management point of view, potentially being able to breed cattle to climb could mean less time spent pushing or fencing them out of lowland waterways and from excessively grazing riparian areas. Improving grazing distribution makes better use of available forage while diminishing concerns about waterway management and protection.
Bailey and others have worked together on three sets of studies on multiple ranches from Montana to Nevada tracking cow movements beginning in 1998 and continuing today. Using Global Positioning System (GPS) tracking data, they were able to sort cattle into “hill climber” or “bottom dweller” groups and then, using genomic testing from blood tests, compare the genomes of the hill climbers and bottom dwellers. What they found were genetic markers for grazing distribution.
“The Single Nucleotide Polymorphism (SNP) array identified five chromosomes that accounted for 35% of the variation in distribution,” explains Bailey. “That’s on par with weaning weight, so we were pretty excited.”
Tons of data to sort through
About one-third of the grazing area of large and rugged pastures goes unused, Bailey reports, which leaves room for substantial increase. It looks like breeding could help reduce some of that waste.
The research, while promising, has presented challenges. For one, almost no pasture is exactly the same in terrain or size. Pastures had to be broken down into characteristics that describe the terrain, among other things, elevation and distance to water, and each animal’s position tracked so that they could be identified as a “hill climber” or not. The cost of GPS technology also required researchers to rotate the collars on cows because they didn’t have enough to go around, adding time to an already lengthy process.
“It is a bear to collect the information,” Bailey shares. “When we first started the second study, the GPS collars were about $1800 a piece. They have come down some in price, but still, they are tracking constantly and giving us a huge volume of data to sort through.”
Dr. Milt Thomas, a professor of beef cattle breeding and genetics at Colorado State University is also a member of the study team. “With this research, the GPS data might include up to 8000 coordinates for just one animal,” he says. “When you have 800,000 genotypes, that’s a big bunch of data to sort through. It is very challenging to identify the best trait for genetic analysis; perhaps it’s how far a cow walks from the water, or how high she climbs, or a combination of the two.”
The researchers have to combine the phenotypic data with genotypic data in order to come up with an estimation of the trait’s heritability. Time consuming, but valuable.
“For every trait, when there’s lots of data it’s easy to determine heritability,” Dr. Thomas maintains. “Weaning weight, for example, is about 30% heritable (nature/genetics) and about 70% environmental (nurture). With behaviors, like grazing distribution, we also have to consider things like memory and learning, but our preliminary research suggests that the heritability of grazing distribution may be similar to weaning weight.”
Climber’s gonna climb
The first set of research, published in 2006, showed that even if the cows identified as “climbers” and those as “bottom dwellers” were separated, the climbing group still made the climb. They didn’t, as some have hypothesized, just fill in the gaps left by the bottom dwellers. This demonstrated that individual animals could be selected to improve grazing uniformity.
In the second study, which was published in 2015, and the third study, which is still ongoing and expected to be complete by next year, researchers tracked cows with GPS at ranches across the western U.S. These studies revealed the genetic markers for terrain use and how genotype and phenotype can be used in association to identify traits. Cattle in previous studies had various breed backgrounds, including Angus, Brangus, Hereford, and Limousin as well as other breed crosses.
“We are almost at the end and we’re really excited,” Bailey remarks with enthusiasm. “The past results were so good, we’re looking forward to the next set of results.”
Though they’re still watching cows and combing through the data from the current study, Bailey envisions their results to be useful and practical for ranchers in the future.
“I think a future genetic test for grazing distribution could have a big impact. A blood test is only about $30, and while it’s not perfect, it could be very helpful for distribution,” Bailey suggests.
At this point, Bailey is pleased to report that the grazing traits don’t have any association with other, less desirable traits, which is positive as well. Just to be sure, the researchers are examining everything from body condition to disposition to see what associations might exist.
“As we have developed genetic technologies, our ability has changed,” shares Thomas. “First we tracked performance data like average daily gain because it was easy to weigh the animals to obtain the phenotype. Now we’re studying how animals fit the environment; it has just taken science a while to catch up. These traits are just as important.”
“Beef production is very different than other types of livestock in that dairy/pigs/chickens have environments that have been altered to best fit the animals,” he adds. “But in beef, we change animals to fit the environment. There’s land out there that we can’t farm in traditional row crop situations, but cattle can graze as forage.”
Whatever traits cows carry, the steps cows take do matter to the health of our rangeland and waterways. Breeding for grazing distribution allows us to take our jobs as stewards, not only of animals but also of the land, literally to the next level.
So, Who Likes to Hike?
In the past, behaviors like grazing and climbing have been observed to differ among breeds. Some breeds, depending on what kind of environment and terrain they developed in, tend to walk farther. That some behaviors are genetically based makes sense.
“All traits in animals are influenced by genetics, so it’s not surprising that behavioral traits are as well,” explains CSU professor Dr. Milt Thomas. “We already measure things like disposition, speed (coming out of the chute), and those things are moderately heritable, so grazing distribution being genetically influenced isn’t really surprising.”
However, finding out that grazing distribution is heritable doesn’t automatically translate to particular breeds. Variation comes from both nature (genetics) and nurture (environment).
“In theory, a breed from mountainous regions would probably be better (at grazing distribution) than those who are not, but it’s very interesting because it’s not always that straightforward,” Thomas surmises. “The whole process of bringing one breed in to a new place can change things. It’s definitely a segment where more research needs to be done.”
