The applicability of pregnancy diagnosis using interferon-stimulated genes in embryo-transferred Japanese Black cattle

The early pregnancy diagnosis method by measuring interferon-stimulated genes (ISGs) in peripheral blood can be used in cattle after artificial insemination (AI) with high accuracy. ISGs are genes whose expression is induced by interferon tau (IFNT) in the trophectoderm of the conceptus during early pregnancy in cattle. We evaluated the applicability of ISG-based pregnancy diagnosis in embryo-transferred (ET) cattle. The diagnostic potential of ISG was assessed using previously established cutoff values for AI cattle. ISG levels in the peripheral blood were measured on days 19 and 21 of gestation, and diagnostic accuracy was calculated. The results showed significantly higher ISG expression in pregnant than in non-pregnant cattle on day 21, but not on day 19. Applying AI cattle threshold values to ET cattle resulted in reduced accuracy, particularly on day 19, compared to AI cattle. These findings suggest that the causes of non-conception may differ between AI and ET cattle. These findings highlight the limitations of using ISG-based early pregnancy diagnosis during the preimplantation period in ET cattle.