Diagnostic Performance of Pregnancy Associated Glycoproteins and Transrectal Ultrasonography During Early Pregnancy Detection

Abstract

2025 Denman Research Forum, 2nd Place in "Insects and Other Animals" category2024 College of Food, Agriculture, and Environmental Sciences Research Forum, 3rd place in "Animal Sciences" categoryEarly detection of pregnancy in ewes is instrumental for providing adequate nutritional requirements as well as efficiency of production and provides producers the opportunity to adjust management practices. Pregnancy associated proteins (PAGs) are produced by binucleated trophoblast cells of the placenta and enter the maternal circulation, effectively serving as a biomarker for pregnancy establishment. The objective of this study was to evaluate the performance of PAGs and transrectal ultrasonography (TRU) for pregnancy diagnosis at 20, 25, and 30 days after breeding. Dorset and Dorset cross ewes (n = 126) were synchronized using a short term CIDR protocol. On day -6 a CIDR was inserted and on day 0, each ewe received a dose of prostaglandin (PG) F2α and placed with fertile rams fitted with marking harnesses. Ewes were monitored twice daily for signs of breeding from day 0 to 4.5. Ewes were evaluated by TRU using an 8.3 MHz linear-array probe (Mylab Delta, Esoate) on days 20, 25, and 30 after breeding to determine the presence of a conceptus (embryo and associated membranes). In addition, blood samples were collected by jugular venipuncture on day 20, 25, and 30 after breeding. Each sample was collected into an evacuated tube, centrifuged and stored at -20 ºC. Plasma samples were assayed for the presence of PAGs using two commercially available enzyme linked immunoassays (IDEXX Rapid Visual Pregnancy Detection and IDEXX Ruminant Pregnancy Test). True pregnancy status was determined by transabdominal ultrasonography at day 125 and lambing date. Diagnostic performance was evaluated using specificity, sensitivity, accuracy and Cohen’s Kappa. Data were analyzed using generalized linear mixed models. Sensitivity (97.8%), specificity (94.4% to 97.2%) and accuracy (98.4% to 98.8%) of TRU was high and did not differ (P > 0.05) between days 20, 25, and 30. Although sensitivity of the Rapid Visual Test (RVT) was high (92.2% to 94.4%) and not affected (P > 0.05) by examination day, both specificity (27.8% to 83.3%) and accuracy (73.8% to 91.3%) increased (P 0.05) among methods at day 30, TRU had greater (P < 0.05) specificity than both RVT and RPT at days 20 and 25. Lastly, accuracy of TRU was greater (P < 0.05) than that of RVT and RPT at all examination days. In conclusion, improved diagnostic performance of TRU makes it the preferred method when performing pregnancy diagnosis before 30 days in ewes. However, the use of PAGs for pregnancy diagnosis appears as a suitable method when diagnosis is performed at 30 days.USDA National Institute of Food and Agriculture, Multi-State Hatch project 1023183 (OHO01496-MRF)IDEXX Laboratories, Inc., Westbrook, MaineA three-year embargo was granted for this item.Academic Major: Animal Science