New Accurate Test for Determination of Pregnancy Status
Posted: March 8, 2005
Palpation of the uterus for the presence of the amniotic vesicle, fetal membranes, uterine fluids (fluctuance), or cotyledons is the method generally used to determine pregnancy status. Although rectal palpation is a relatively simple and inexpensive procedure for those who acquired this skill, there are some shortcomings. As with any technique, there is variation in palpating skill among practitioners. Secondly, since several research studies have shown conflicting evidence concerning the magnitude of embryonic death caused by palpation of the amniotic vesicle or the membrane slip method, one cannot ignore the possible effect of palpation on embryonic loss.
For many years real-time transrectal ultrasonic imaging has been a tremendous research tool for reproductive physiologists. Within the last several years some dairy practitioners have applied this technology for diagnosis of pregnancy status. The embryo can be detected earlier than by palpation and ovarian structures can be visualized. There is minimal handling of the reproductive tract during ultrasonography, thus the chance of inducing embryonic mortality is reduced. Although this technology is expensive, modifications have been made so that the equipment is more adaptable to the farm environment. As further modifications to the equipment are made and dairy producers realize a benefit from applying this technology ultrasound will likely be used more routinely.
A third method of determining pregnancy status has been developed. In the cow, pregnancy-specific protein B (PSPB), produced by specific cells of the placenta was isolated in the mid 1980’s by Dr. Sasser at the University of Idaho. He developed a radioimmunoassay (RIA) to measure PSPB during various stages of pregnancy and verify the accuracy of this method for detecting pregnancy. Initial research published in 1988 using a radioimmunoassay has shown this assay to be 100% accurate for identifying non pregnant cows 30-35 days following insemination and greater than 90% accurate in determining pregnancy. Newer technology for detecting PSPB has now been commercialized and available to dairy and beef producers. The new assay is termed BioPRYN™ and the accuracy in determining overall pregnancy status on a herd basis is 97%. Accuracy, when a cow has the test result of open, is nearly 100%; when the test result is pregnant, accuracy is 91 to 95%. This is not a cow-side test. Blood samples are obtained from the tail, refrigerated if kept overnight or are shipped immediately without ice to the laboratory. The results are returned the next working day after receiving the sample via FAX, email, phone or mail. The cost is $1.95 per sample. It is recommended that blood samples be obtained at 30 or more days after insemination for heifers or lactating cows. Since there is residual PSBP in the blood from the previous pregnancy, the earliest lactating cows can be sampled is 90 days after calving. This would mean any cow inseminated beyond 60 days post partum would be eligible for pregnancy determination with this method if samples were obtained 30 days post insemination (total 90 days).
With most estrous synchronization timed-insemination programs cows are targeted to be inseminated around 70-75 days. In this situation, blood samples for PSPB analysis would be obtained at 100-105 days. With the embryonic loss in cattle estimated to be between 15-20%, one might question if residual PSPB would be present in the blood when the sample was taken approximately 30 days post breeding but the embryo died during this period. The assay is developed so that the concentration of PSPB can be quantified. The results are reported as pregnant, pregnant with repeat sample, open with repeat and definitely open. Those few cows requiring repeat samples may have lost their embryo and a submission of a second sample would verify pregnancy status. Some dairy producers are submitting samples from cows again at 70-80 days following early pregnancy confirmation at 30 days to verify maintenance of pregnancy. One must appreciate the value of early determination of the non pregnant cows. Since post breeding heat detection is generally poor on many dairies resulting in long intervals between inseminations, this non invasive method of identifying open cows allows dairy producers to resynchronize open cows as a group.
There are four laboratories established in the U.S. where blood samples can be submitted for analysis using this new method termed BioPRYN™. Check the following website for more detailed information describing this concept and procedures for submission of samples: BioTracking LLC website
This is another tool for reproductive management which
can be used to determine pregnancy status early enough
so open cows can be managed to be rebred in a timely
Michael O’Connor, Dairy and Animal Science Extension