Can high-altitude genetics stem high-dollar cattle losses?
June 1, 2017: Two bovines escape from a pasture. They’re rounded up and secured in a pen. It’s not the first time. Escapees A130 and A330 are half cow, half yak, bred as part of a study on brisket disease and altitude adaptation in cattle.
The short of it is at high altitudes, some cattle get sick and some die. The higher the altitude and longer they stay – on summer pastures or ranches above 6,000 feet, for example – the worse the problem. Oxygen deficiency causes the arterioles, the tiniest arteries in the lung, to constrict, which makes the heart’s right ventricle work harder. A cow with brisket disease, also known as bovine high-mountain disease, may develop swelling and fluid buildup (edema), especially in the lower chest area, or brisket.
Coming from molecular biology and genomics is Mark Stayton, who retired as an associate dean in the College of Agriculture and Natural Resources in July. His approach to brisket disease is to isolate the genes responsible, develop a quick blood test to tell if cows are susceptible, and start a new line of cattle using interspecies breeding.
The plan at the Laramie Research and Extension Center (LREC) is to selectively breed first-generation (F1) cattle-yak crosses to cattle for multiple generations until the cows are back to being almost entirely cows again – but with some of the altitude resistance that allows domestic yaks to survive at 14,800 feet on the Tibetan Plateau.
Travis Smith, livestock manager at the Laramie Research and Extension Center, says after securing the errant half-yaks in a holding pen, “I’ve never seen anything like it. They’re wild one minute and coming up to you, nuzzling your leg and nipping at your horse’s tail the next.”
The nine heifers and five bulls in the study represent the elite 21 percent born a year ago after 66 of the center’s mixed Hereford-Angus cows were artificially inseminated with yak semen.
Enter Talbotts’ Brae Arden Herefords
April 7, 2017: Veterinarian Timothy Holt of Colorado State University arrives at the LREC beef unit at 7:45 a.m. with a field team of four vet students. Next to the squeeze chute in the large metal building, they set up tables, a series of brightly colored disinfectants, oscilloscope, and supplies for pulmonary arterial pressure (PAP) testing.
Cattle growers for years have selected for altitude-resistant animals using PAP testing. A low PAP score, the average of the systolic and diastolic blood pressures, indicates an animal is pumping blood through the lungs easily.
When Janet Talbott and her son, Jay, learned Holt would be in town for the yaks, they arranged to bring in five of their Brae Arden Herefords. The Talbott ranch, about seven miles from the LREC, lies at more than 7,200 feet. Jay Talbott once bought a top sire in Nebraska. After 60 days of acclimation, he had it PAP tested and had to send it back.
In places like Nebraska and Texas, the trend is for bigger, blockier animals, improvements that can be costly in the “Brisket Disease Belt” of Colorado and Wyoming. Holt has reported calf crop losses as high as 65 percent in susceptible cattle and says losses of 25 percent are not uncommon.
The Brae Arden Herefords originated from a train car load Janet Talbott’s father bought at the National Western Stock Show in Denver in the 1930s. The family’s breeding program has never strayed from the original line, which has kept the herd genetically closed for almost 90 years.
As the Hereford bulls fill the chute, Talbott comments, “They’re so docile, you practically have to twist their tails to get them to move.”
The motor for the hydraulic head chute churns, the overhead line lets out an intermittent chu, and the radio in the office window plays classic vinyl.
The two panels of the head catch close on the first Hereford. Grandson Jaymes Talbott halters him and pulls the lead rope around the squeeze chute until the cow’s right horn touches the metal panel. This awkward head grab, or “mugging,” exposes the target of Holt’s needle.
The jab into the vein is strong and sure. Holt feeds tubing through the needle hub into the right ventricle and up the pulmonary artery, which leads from heart to lung. The transducer at the tip converts the pulmonary blood pressure to an electrical current. At 7,200 feet, they’re looking for a PAP measurement of 40 or less. All present turn to the oscilloscope screen.
The Hereford’s score is 36.
Talbott responds matter-of-factly, “I’d be surprised if it were any different.”
The head catch is released. Holt calls, “Coming out the chute!” and the bull runs through the open doorway.
Next Up, Yaks
Holt: “OK Kelly, you’ve got the squeeze. Belle, sticking. Amanda, passing.”
Holt stands close. Jaymes Talbott stays on as mugger. Belle Belden jabs the jugular vein, and Stayton, wearing sky-blue nitrile gloves, extends a vial under the thin, red stream.
The blood of the control cows and yak-crosses in this and future generations will be used to sequence the DNA and segregate the genes for resistance.
Amanda Blassingame starts the arterial line. Holt calls out the first bovine (cow) score: 37.
Haley McKee, a UW molecular biology student, records the PAP for each animal, along with the systolic and diastolic pressures.
There are no docile yaks. As A130, a steer, approaches the tailgate of the squeeze chute, he spots a gap and runs. In the head squeeze, Yak Z341 pulls and shakes vehemently, finally dropping to its knees. Holt pushes, Talbott pulls, and Kelly Kolar at the chute lever adjusts until at last, mugger, headgate, and yak align. McKee writes “problem child!” after the score of 35.
“So far, so low,” calls Holt.
Bovine X207 proves to be the outlier at 66.
Yak A206, another escapee, comes up again. PAP score: 39.
“That’s a regular random cow. No love for that one,” says Holt to the next cow through. PAP score: 36.
Yak A130, one of three that got away, is last. After following the fences to the corral, he is back in the chute, nervous and wary.
In the end, the averages are Bovines 42: Yaks 34.
Stayton Widens the Score
August 2, 2017: A two-ton UW truck creeps over rocks and washboard earth, hauling a 1,600-gallon plastic tank to the top of a mountain road. It’s a test run. Smith expects to make this trip with 12,800 pounds of water and 3,200 pounds of hay (two round bales) to 10,000 feet every two or three days until October.
Stayton wants to expose the cows and F1 yak-crosses, now 14 to 16 months old, to what he calls super-high altitude. He wants to really stress them. In the fall, the CSU livestock field unit will perform PAP testing on the mountain. The hypothesis is the stress will hit the bovines hard, while the yaks live in ease.
In the end, however, altitude resistance is only useful to Wyoming ranchers if the new animals also express the traits necessary for efficient beef production. Fortunately, the first yak-bovine crosses show potential as commercial stock.
To keep the cows and yak-crosses in, Smith and crew will erect rugged 6-foot-high fence panels, the kind used to contain rough stock – rodeo broncs and bulls. At the beef unit, Smith has watched yaks walk up to a wire fence, stand flat-footed, and jump over. He returns the yaks, only to have them escape again before he can unsaddle his horse.
Yaks, Bos grunniens, and cattle, Bos taurus, have been crossed in Tibet for 3,000 years. According to Stayton, their protein sequences are, on average, 99.5 percent identical. It is within that .5 percent difference that things get interesting.