Pregnancy blood tests prove to be reliable, cost-effective
Blood tests that detect bovine pregnancy 28 or 29 days after breeding are catching on fast.
While some of the companies providing the tests are reluctant to release numbers, it’s a safe bet that close to a million of the tests were run last year alone. BioTracking LLC and its affiliates ran 733,000 tests in 2011, says Garth Sasser, the company’s president.
Why all these tests? They’re easy, reasonably priced and pretty darn accurate. Though it takes a few days to get results back, primarily due to shipping time on the front end, producers can work the testing regime into their normal reproductive management schedule.
The best way to use these tests is to integrate them into your resynchronization schedule, says Paul Fricke, a University of Wisconsin reproduction specialist.
"For example, if your resynch protocol calls for giving a setup shot of GnRH at 32 days postbreeding, you can pull a blood sample on Tuesday or Thursday of that week and send it in. By Monday, you’ll have the test results and can go ahead with the rest of the resynch program if the cow is open," he says.
The ELISA-based tests detect pregnancy-associated glycoproteins. They can start to be detected in the dam’s blood 25 days after breeding, though most tests’ label directions recommend waiting 28 or 29 days.
However, glycoproteins from previous pregnancies remain in the bloodstream for several months after calving. So most tests recommend waiting at least 60 days, and some up to 90 days, following calving. (Heifers, because they have had no previous pregnancy, don’t merit this concern.)
Herds with a 50-day voluntary wait period can be on the cusp of a 90-day window, depending on their presynch program, Fricke says. "The key is to look at the directions on the blood test kits and follow them," he says. "If you do, you should be OK."
"We palpate very little, unless we’re unsure of the test results," says Johan Vosloo, manager of Country Dairy in New Era, Mich., who has been using the tests since 2006. "But those cases are very few and far between. There’s no really no reason to palpate.
"And that opens up valuable time to let our veterinarian be more of a consultant than simply a glorified arm. We rely on the blood tests to tell us which cows are open, and we tell our vet to look at that specific cow," Vosloo says. "That allows him to focus on infertility issues, not fertility."
Vosloo tests cows three times. "Our P1 test is done at 30 to 36 days after breeding," he says. Doing it a few days later than the bare minimum of 28 or 29 days helps catch a few more cows that might have lost fetuses that were present early.
Vosloo does his P2 test at 65 to 70 days to catch the cows that have lost pregnancies since the first test. He also aggressively watches for heats, including the cows in early pregnancy, trying to catch those that come back open before their P2 test. By the time he does his P2 test, only 2% to 3% will come back open.
He does his P3 test at dryoff to ensure he’s carrying no open cows into the dry period.
The key to all of this is accuracy. "You need accurate lists of cows to be tested," he says. And you need to be able to find those cows easily.
Country Dairy’s 1,400-cow herd is split among four barns. The largest houses 520 cows. "We have relatively small barns, so we can go into a specific breeding pen and usually pull a blood sample as the cow lies in the freestall," Vosloo says.
"For a high-strung cow, we might have to catch her, give her a few minutes to chill out and then draw blood," he says. "The needles we use are only 20 gauge, and it really doesn’t bother them much."
But again, accuracy is key. Before shipping, Vosloo always double-checks his computer list against his blood vials.
Jonathan Odell also waits a bit longer to confirm pregnancies, usually 40 days or so postbreeding. He has been using blood pregnancy tests for about a year.
Odell, who milks 520 cows near Panama, N.Y., with his son, Bill, says he’s achieving better than 60% conception rates. "If we went at 29 days, we might get a 40% eventual conception rate because of lost pregnancies," he says. Pregnant cows are tested again 40 days later to confirm the pregnancy.
Odell’s test results are e-mailed to his Genex breeder, who then enters the information into his computer.
"We’ll pull blood on Monday or Tuesday, get the final results back on Friday and resynch open cows the next Tuesday," Odell says.
At first, Odell thought that pulling the blood samples, tracking and shipping them would be a hassle. But he’s been able to take blood samples right in the parlor after milking. "I really like the convenience; one man can do it easily," he says.
Links to commercial tests: