Establishment of a latex immunochromatography for detecting bovine early pregnancy-related glycoproteins

Early pregnancy diagnosis in dairy cows is an important part of the production processes. Accurate early pregnancy diagnosis can help veterinarians identify open cow as soon as possible and carry out the second breeding earlier, which is of great significance for improving reproductive efficiency of dairy cow. In this study, a rapid immunochromatography based on latex microspheres for detecting pregnancy-related glycoprotein (PAG) was established with two monoclonal antibodies. The samples collected from 28 days after breeding of 559 Holstein cows were used to diagnose pregnancy. The results showed that the minimum detection limit of the established latex immunochromatography for PAG was 0.2 ng/mL. Compared to ultrasound, the sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of this method for pregnancy diagnosis was 99.25%, 90%, 91.03%, 99.15%, and 94.68%, respectively, and the kappa value is 0.89, which demonstrated that the pregnancy diagnosis results of the test strip method have high consistency with ultrasound. Compared with commercial enzyme-linked immunosorbent assay (ELISA) kits, the positive coincidence rate, negative coincidence rate, and overall coincidence rate of this method was 98.29%, 97.6%, and 98.03%, respectively. This indicated that the test strip has high consistency with the currently widely used ELISA immunological diagnostic method. The latex immunochromatographic method established in this study can accurately diagnose pregnant cows and can be used for early pregnancy diagnosis of dairy cows. The method is simple to operate and fast to detect, and the results are easy to interpret, which is of great significance and clinical application value for cow early pregnancy detection. KEY POINTS: • A rapid immunochromatography based on latex microspheres with two monoclonal antibodies specific to PAG2 was established for early pregnancy diagnosis of dairy cows. • The early pregnancy test method, which we have developed, exhibits high sensitivity and can be utilized in small to medium-scale ranches. • The clinical sample test results demonstrated that the test strip has a high degree of consistency with ultrasound.