As cow-calf producers are selecting bulls for this year’s breeding season, they know that getting their brood cows bred is critical. And when a cow is confirmed pregnant, her position in the herd is solidified as a valuable contributor to next year’s calf crop. While palpation and ultrasound are commonly used methods to determine pregnancies, blood testing is another option worth considering. According to Zen Miller, Outagamie County UW-Extension agricultural agent, new options for blood pregnancy tests can offer costs savings and additional benefits to cattle producers.
Determining whether a cow is pregnant is important for making marketing decisions, Miller explained to cow-calf producers at a meeting in Kaukauna earlier this month. Producers may choose to cull open cows to cut down on the cost of overwintering cows that are not going to produce a calf. “If a cow is open, you don’t need to feed her all year,” Miller said. If selling stock cows to other producers, it is important to the buyer to know whether or not that cow is carrying a calf. Further, knowing each cow’s pregnancy status allows producers to provide prompt return service to tighten the calving season for next year.
Traditional determination methods like palpating and ultrasounding are typically done on the farm by a veterinarian. While these methods offer other benefits like sexing the fetus and predicting calving time, a visit out to the farm generally incurs both a trip charge and hourly rate. Given that the majority of cow-calf operations in Wisconsin are smaller herds with fewer than 50 cows, those costs can add up.
Recently, blood pregnancy tests have become commercially available to cattle producers. These blood assays test for the presence of a specific pregnancy-related protein. Miller discussed three available tests that producers may want to consider implementing in their reproduction protocols: BioPRYN, DG29 and IDEXX. Producers can purchase do-it-yourself blood collecting supplies and kits for these specific tests. While there is some variance in cost, the range for testing is around $3.00 to $4.00 per head. On some operations, this may offer cost –per-head savings over their current pregnancy checking program.
One of the benefits of blood pregnancy testing is that a pregnancy can be confirmed earlier than through palpation. These tests can be conducted in the range of 28 to 30 days post-breeding, which is five to seven days earlier than rectal palpation. It is recommended that producers wait 90 days post-calving to pull samples to ensure that any residual levels of pregnancy proteins from carrying the previous calf are no longer present, which could result in false positive results. Ultimately, shortening the time elapsed between breeding and pregnancy checking can help cow-calf producers improve reproductive efficiency by reducing days open and more promptly performing return servicing or synchronization.
Once a sample has been taken, it is then mailed to a testing laboratory designated by the company supplying the test. Multiple laboratories are located in Wisconsin, offering producers here the advantage of less transit time for samples to travel through the postal system. The actual testing time for these samples ranges from a few hours to 48 hours. Results can then be communicated back to the producer quickly via telephone, email or fax. Again, these quick results can help producers to streamline their reproduction programs and make more informed management decisions on culling and breeding.
Producers may also find benefit in using the pregnancy blood sample to test for other diseases. With these tests, a small amount of blood is drawn from under tail, usually a minimum of 2 milliliters. For an additional cost, that one sample can also be tested for multiple diseases like Johnes and bovine viral diarrhea (BVD). Using a single sample to test for multiple diseases can cuts down on handling time for the producer.
While there are potentially several advantages to using a blood pregnancy test, Miller also noted the disadvantages as well. Because there is a period of time that could be several days between collecting samples and receiving results, cattle will likely need to be handled more than once. After the producer has their results, he or she will have to sort and group animals again, adding to cattle handling time and labor.
When proper sampling instructions are followed, these blood tests are 99 percent accurate at identifying open cows. This accuracy is of high importance because when a cow is confirmed open, the producer may choose to carry out reproductive protocols like giving prostaglandin. If a cow were incorrectly identified as open and given a shot, it would cause her to abort her calf, resulting in further delay in the reproductive cycle and additional cost to the producer. The false-positive (false pregnant) rate for blood pregnancy tests is in the range of 5 percent, which can often be attributed to early embryonic death that occurred prior to or at the time blood was collected.
With high levels of accuracy and low per-head costs, Miller told producers that blood pregnancy testing has the opportunity to be a tool in making culling and management decisions.