ISG-based pregnancy diagnosis shows reduced accuracy in embryo-transferred cattle, especially on Day 19
Background
Accurate early pregnancy diagnosis is critical for efficient reproductive management in cattle farming, enabling timely re-breeding of non-pregnant animals. Maternal recognition of pregnancy (MRP) in ruminants relies on interferon tau (IFNT), secreted by the conceptus, which prevents luteolysis by suppressing uterine prostaglandin F2α (PGF2α) pulses. This IFNT signal induces the expression of interferon-stimulated genes (ISGs) in maternal peripheral blood, serving as a non-invasive biomarker for pregnancy. While ISG-based methods are highly accurate for artificially inseminated (AI) cattle, their applicability and reliability in embryo-transferred (ET) cattle have not been thoroughly evaluated, representing a significant gap in current diagnostic protocols.
Study Design
Researchers evaluated the diagnostic utility of ISG levels in embryo-transferred (ET) Japanese Black cattle. Peripheral blood samples were collected from ET cattle on Day 19 and Day 21 of gestation. ISG expression levels were measured and compared between pregnant and non-pregnant animals. Diagnostic accuracy was calculated using both previously established threshold values derived from AI cattle and new threshold values specifically calculated for ET cattle using the Youden index from receiver operating characteristic (ROC) curves. The study aimed to determine if ISG levels could reliably predict pregnancy in this specific population.
Results
The study found that ISG expression was significantly higher in pregnant ET cattle compared to non-pregnant ET cattle on Day 21 of gestation. However, this significant difference was not observed on Day 19. Regardless of whether AI cattle-derived or ET cattle-specific threshold values were applied, the diagnostic accuracy of ISG-based pregnancy testing in ET cattle was reduced, particularly on Day 19, when compared to the known high accuracy in AI cattle. This suggests a potential difference in the timing or magnitude of the IFNT signal, or the maternal response, in ET cattle.
Key Findings
- ISG expression was significantly higher in pregnant vs. non-pregnant ET cattle on Day 21.
- No significant difference in ISG expression was observed between pregnant and non-pregnant ET cattle on Day 19.
- Diagnostic accuracy of ISG-based pregnancy testing was reduced in ET cattle compared to AI cattle.
- Reduced accuracy was particularly pronounced on Day 19 in ET cattle.
- Findings suggest differing causes of non-conception between AI and ET cattle.
Why It Matters
For cattle breeders and veterinarians managing embryo transfer programs, these findings highlight a critical limitation: ISG-based early pregnancy diagnosis, while effective for AI cattle, may not be reliably applied to ET cattle at the same time points. Protocols for early pregnancy diagnosis in ET cattle may need to be adjusted, potentially requiring later testing (e.g., Day 21 instead of Day 19) or the integration of additional diagnostic markers. This research suggests that the physiological mechanisms underlying non-conception might differ between AI and ET cattle, necessitating tailored diagnostic approaches for optimal reproductive management. Further research is needed to identify these differing causes and develop more accurate, ET-specific diagnostic tools.
pregnancy-diagnosis
interferon-stimulated-genes
cattle
embryo-transfer
reproductive-health
animal-husbandry