Interferon-tau concentration at the vaginal fornix and cervical ostium predicted early pregnancy outcomes in lactating dairy cows†.

Concentrations of interferon-tau (IFNT) are likely the best proxy for early pregnancy diagnosis in cattle. Objectives were to compare the concentration of IFNT at the vaginal fornix and cervical ostium 18 days after artificial insemination (AI) and evaluate the use of IFNT for early identification of non-pregnant lactating dairy cows. Holstein cows (n = 251) from two dairies were enrolled. Expression of interferon-stimulated gene 15 (ISG15), myxovirus 2 (MX2), and viperin (RSAD2) were assessed in peripheral blood mononuclear cells (PBMC) by RT-qPCR. Expression of interferon-stimulated genes (ISG) and IFNT concentration in swab samples collected at the cervical ostium and vaginal fornix were measured by RT-qPCR and sandwich ELISA validated for bovine IFNT, respectively. Cervical IFNT concentration was 7.5-fold greater than the vaginal fornix on day 18 after AI in cows diagnosed as pregnant by ultrasonography on day 35 after AI. Concentrations of IFNT in the cervical ostium and vaginal fornix were positively correlated with ISG expression in cervical cytology of pregnant cows, however, ISG expression in PBMC was not correlated with cervical IFNT concentration. Assessment of cervical IFNT concentrations for identification of non-pregnant cows on day 18 after AI yielded reasonable specificity (0.84; 95% CI = 0.78-0.90) and negative predictive value (0.87; 95% CI = 0.81-0.93) based on ultrasound examination on day 35 after AI. These results support the feasibility of using cervical IFNT measurement for identification of non-pregnant cows, providing the basis for early resynchronization and increased insemination rates in dairy farms.