Identification of embryonic/fetal mortality in cows by semi-quantitative detection of pregnancy-associated glycoproteins

Late embryonic and early fetal mortality (EM/FM) might occur following a pregnancy diagnosis, decreasing the accuracy of pregnancy diagnostics in dairy cattle. Therefore, the detection of EM/FM may be useful in dairy reproductive management. Comparatively low concentrations of pregnancy-associated glycoproteins (PAGs) have been previously associated with EM/FM. The aim of the present study was to test the ability of a semi-quantitative enzyme-linked immunosorbent assay for the detection of PAGs (PAG-ELISA) to either diagnose (EM/FM has already occurred) or to predict (EM/FM will occur) EM/FM. Three experiments were carried out as follows: (1) PAG-ELISA validation, (2) a retrospective verification of 141 FAG results in cases with suspected EM/FM and the identification of cut-off values for EM/FM, and (3) a field experiment, testing the proposed PAG-ELISA cut-off values defined in Experiment 2 under farm conditions by comparing transrectal ultrasound (TRU) results with PAG-ELISA results. The PAG-ELISA validation (Experiment 1) demonstrated that an optical density (OD) range of 0.4-2.8 reflected a linear relation to the PAG concentrations. The results from Experiment 2 indicated that more cows (85.7%) with PAG-OD values ranging from 0.40-0.79 showed EM/FM compared to cows (21.7%) with PAG-OD values ranging from 1.2 to 1.5. A cut-off value of 2.2 (sensitivity [SEN]=87.6%; specificity [SPE] =72.8%) was determined using ROC-curve analysis for prediction of EM/FM and a cut-off value of 1.2 for diagnosis of EM/FM (SEN=50%; SPE=94%). However, in the field experiment, EM/FM was best diagnosed using a cut-off value of 1.5 (SEN=26.7% and SPE=96.5%). Hence, the high SEN detected in Experiment 2 could not be confirmed in the field experiment indicating that a singular FAG value is not a convenient tool to diagnose EM/FM. Though, the combined use of PAG-ELISA and TRU showed remarkable results (SEN=84.2%; SPE=98.1%) by revealing a technique for diagnosis of previously occurred EM/FM and for prediction of subsequent occurring EM/FM.