Commercially available blood tests offer reliable pregnancy detection and are similar in accuracy to transrectal ultrasound, reported Paul Fricke, University of Wisconsin dairy reproductive specialist, at the 2011 Dairy Cattle Reproductive Council Annual Meeting in Kansas City, Mo.    

Data from multiple field trials show commercial tests that detect pregnancy-associated glycoproteins (PAG) offer acceptable sensitivity and specificity, as well as a high negative predictive value. Furthermore, commercial PAG and pregnancy-specific protein-B (PSPB) tests may more reliably detect animals undergoing pregnancy loss compared to transrectal ultrasound. 

However, it is imperative to follow all manufacturer directions when using any of these tests so animals are not subjected to nonpregnancy testing too early postpartum and users avoid false-positive results. Proper test timing also ensures that cows and heifers are not tested too early post insemination, to avoid poor sensitivity, specificity and accuracy of the test.

Source:  Dairy Cattle Reproduction Council