Adult female bison don’t take kindly to traditional pregnancy tests.
The test, known as “rectal palpation,” involves a veterinarian inserting a gloved arm to feel for thickening in the uterus wall. In hormonal beasts weighing nearly 1,200 pounds, the test can quickly become a recipe for injuries.
“Buffalo are tremendously fast and strong,” said Dr. Kenneth Throlson, a retired vet who owns a North Dakota bison ranch. “They go from docile to crazy in about two snaps of the finger.”
About seven years ago – after two hip replacements, back injuries and shoulder troubles – Throlson switched from manual pregnancy testing to blood tests for the ranch’s 300 bison cows. Blood samples are sent to BioTracking LLC in Moscow, Idaho, for processing. Within 27 hours, ranch hands know which bison are pregnant.
“If we get the samples today … we can tell the farmer tomorrow in the afternoon,” said Dr. Garth Sasser, BioTracking’s president. “Our tests are 99 percent sure if we say she’s not pregnant and 93 to 95 percent correct if we say she is pregnant.”
Sasser and colleagues at the University of Idaho originally developed the test for cattle in the 1980s. While domestic livestock accounts for the bulk of the company’s sales, pregnancy tests for wildlife and farm-raised game are on the rise.
Last year, BioTracking processed about 3,200 pregnancy tests for bison, elk, moose, deer, big horn sheep and exotic deer – animals known as “ruminants” because of their multi-chambered stomachs. The tests cost about $20 per animal.
In Oregon, Wyoming and Idaho, the blood tests are being used in research to determine whether wolf packs and ATVs are affecting pregnancy rates in wild elk herds. At ranches such as Throlson’s bison farm, the tests play an important role in herd management.
Producers need to know as quickly as possible if their animals are pregnant, Throlson said. Expectant mothers are put out to pasture, while infertile bison are fattened up for slaughter.
“There’s no free lunch,” Throlson said. “If a cow is not going to have a calf, you turn her into cash in the form of meat.”
Sasser, a UI professor emeritus, grew up on diary farm near Blackfoot, Idaho. BioTracking grew out of his research work. Sasser identified a protein that shows up in cows’ blood 20 to 30 days after conception. He and his associates developed the pregnancy test for cattle and expanded it to wild ruminants. The test uses enzymes to detect the protein in the blood.
BioTracking is the only U.S. firm that confirms pregnancy through blood samples for cattle and wildlife, Sasser said, although some ranchers and biologists also use portable ultrasound machines.
“When they immobilize them with tranquilizers, they can easily take a blood sample,” Sasser said. “Once they know the pregnancy rate, they know a lot about the viability of the herd.”
Each winter, the Starkey Experimental Forest and Range sends BioTracking about 200 blood samples from its wild elk herd. The research area southwest of La Grande, Ore., is run by the U.S. Forest Service and the Oregon Department of Fish and Wildlife.
“We check pregnancy rates as a matter of routine,” said Brian Dick, Starkey Project Area manager. “Pregnancy is an important variable in research. Say you did some logging to reduce fuels in the forest or changed the hunting strategy. You’ll want to know whether that changed pregnancy rates.”
At the moment, Starkey researchers are studying whether driving ATVs through elk habitat decreases the herd’s pregnancy rate.
Before the blood test was developed, researchers at Starkey calculated pregnancy rates by harvesting 25 elk cows each winter. Blood tests allow researchers to expand the sample size, which more accurately projects the numbers of expecting elk, Dick said.
The states of Idaho and Wyoming also use BioTracking’s pregnancy tests to monitor wildlife populations. When elk numbers in the Lochsa River drainage began dropping during the late 1990s, Idaho Department of Fish and Game officials began tracking the herd’s pregnancy rate. The research eventually pointed to low calf weights at birth and bear predation as factors in the herd’s decline, said Craig White, a senior wildlife research biologist.
A recently completed study of 500 mule deer and 500 elk in Idaho also looked at pregnancy rates. As wolves expand their territory in Idaho, the baseline data will help biologists study wolves’ impact on elk herds, White said.
In Wyoming, researchers are using blood sampling and portable ultrasound machines for similar studies on 4,000 elk that roam between Yellowstone National Park and the community of Cody. Part of the herd that migrates into Yellowstone has lower pregnancy rates than elk that hang out in agriculture fields near Cody, said Arthur Middleton, a University of Wyoming doctoral student.
Drought, as well as the wolves’ presence, could account for the discrepancies, he said.
“It’s a complicated set of questions that people badly want to know the answers to,” Middleton said.
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