Evaluation of a Novel Pregnancy Test for Cattle

 

C. S. Whisnant, J. T. French, D. J. Bush, E. A. Coite, J. P. Cassady, S. P. Washburn and A. A. Meier

 

Abstract

This experiment was designed to test the accuracy of a commercially available bllod test for pregnancy in cattle (Biopryn). The test is designed to detect a protein produced by the conceptus (Pregnancy Specific Protein B, PSPB). Blood samples were taken from cows 28-40 days after insemination and at the same time ultrasonography was performed to detect pregnancy. Cows were rechecked via palpation after 60 days post insemination. Blood samples were also taken from cows known to be open including some cows between 30 and 80 days postpartum. Blood samples were sent to the commercial laboratory for diagnosis using the Biopryn test. Comparison of Biopryn results with ultrasonographic results confirmed by later palpation revealed that the test determined the status of cow correctly 93.5% of the time. The test continues to detect the protein in blood of open postpartum cows for 60 to 70 days. Cows less than 60 days postpartum (n = 17) all tested as pregnant using Biopryn. For cows 74-80 days postpartum (n= 5) all tested as open. In a group of cows (n = 6) between 60 and 70 days postpartum some were classified as pregnant and some as open by the Biopryn results. The test appears to be accurate and could be used as long as cows were more than 70 days postpartum when tested.

 

Introduction

Detection of pregnancy in cattle offers valuable information to producers. In dairies it is desirable to know as soon as possible if a cow is open so that she can be treated and re-bred. Days open after the voluntary waiting period are a significant cost to dairy producers. Beef producers could benefit from knowing at weaning if the cow is open and should be culled or pregnant and be retained. Earlier pregnancy detection could identify calves produced by artificial insemination or by clean-up bulls. Currently there are two methods for pregnancy detection: rectal palpation and ultrasonography. Both require skilled and experienced personnel, usually a veterinarian, to perform the tests and the cost may be prohibitive for some producers. A novel blood test for detection of pregnancy in ruminants has been marketed, under the trade name Biopryn (Biotracking, Moscow, ID). The test reportedly detects the presence of a protein known as Pregnancy Specific Protein B (PSPB) in the blood using an enzyme linked immunoabsorbent assay system. Research in the scientific literature using radioimmunoassay to detect PSPB has demonstrated that this protein is produced by the embryo and is detectable beginning approximately 28 days after insemination. The publications have suggested that the protein persists for some time in the blood of postpartum cows. The company has marketed its test as being able to detect the protein similar to the radioimmunoassay. The objective of this experiment was to determine the accuracy of the test and the time frames when the test can be used.

 

Materials and Methods

This experiment was conducted at two research stations, the North Carolina Department of Agriculture Cherry Hospital Research Farm in Goldsboro and the Upper Piedmont Beef Research Unit in Reidsville. Blood samples were taken from cows via tail vein puncture 28-40 days after insemination and at the same time trans-rectal ultrasonography was done to detect pregnancy. Ultrasonography was performed using an Aloka 550V unit (Aloka. Wallingford, CT) equipped with 5.0 megahertz linear array probe. Cows were rechecked via palpation after 60 days post insemination. If there was a discrepancy between the ultrasound and Biopryn results at Upper Piedmont the cows were rechecked by both methods. Blood samples were mailed to the BioTracking laboratory in Moscow, ID. Currently the test can only be performed in this facility. Results from the Biopryn test were compared with results from ultrasonography in the case of the cows that had been inseminated. Because published research indicated that the PSP-B continued to circulate in the blood of cows for some time after calving, blood samples were taken from cows that were between 30 and 80 days postpartum and had not been exposed to bulls or inseminated. 

 

Results and Discussion

Comparison of Biopryn results with ultrasonographic results confirmed by later palpation revealed that the test determined the status of cow correctly 93.5% of the time. The accuracy is favorable and the use of the Biopryn test requires less skill (collection of a blood sample) than ultrasonography or palpation.

In the open early postpartum cows the test continues to detect the protein in blood for 60 to 70 days. Cows less than 60 days postpartum (n = 17) all tested as pregnant using Biopryn. For cows 74-80 days postpartum (n= 5) all tested as open. In a group of cows (n = 6) between 60 and 70 days postpartum some were classified as pregnant and some as open by the Biopryn results. This suggests that use of the Biopryn test should be restricted to cows more than 70 days postpartum to avoid false positives. In practice this is not likely to be a problem since most beef cattle would not be re-bred until 45-50 days postpartum at the earliest and most dairies observe a 50-60 day voluntary waiting period before rebreeding. Adding to these dates the 28 days after insemination before the protein levels are detectable would put cows past the 70 days postpartum when the protein from the previous pregnancy has disappeared.

The timing of detection by the Biopryn test (28 days post insemination) is similar to the earliest detection by ultrasonography and slightly earlier than that of rectal palpation (30-35 days). The test does not require any equipment beyond a needle and tube for blood collection. These results indicate the Biopryn test is accurate and may offer producers another option for detection of pregnant cows in their herds.