RESUMEN
Pregnancy loss (PL) in lactating dairy cows disrupts reproductive and productive efficiency. We evaluated the expression of interferon-stimulated genes (ISG) in blood leukocytes, vaginal and cervical epithelial cells, luteolysis-related genes, progesterone, and pregnancy-associated glycoprotein (PAG) profiles in lactating dairy cows (n = 86) to gain insight about PL. Expression of ISG on d17, d19, and d21 was greater in cows that maintained the pregnancy (P33) compared to nonpregnant with no PL (NP). Greater ISG differences between groups were observed in the cervix (96.7-fold) than vagina (31.0-fold), and least in blood leukocytes (5.6-fold). Based on individual profiles of ISG and PAG, PL was determined to occur either before (~13%) or after (~25%) d22. For cows with PL before d22, ISG expression was similar on d17 but by d21 was lower and OXTR was greater than P33 cows and similar to NP; timing of luteolysis was similar compared to NP cows suggesting embryonic failure to promote luteal maintenance and to attach to the endometrium (no increase in PAG). For cows with PL after d22, ISG expression was similar to P33 cows on d17, d19, and d21 and luteolysis, when it occurred, was later than NP cows; delayed increase in PAG suggested later or inadequate embryonic attachment. In conclusion, PL before d22 occurred due to embryonic demise/failure to signal for luteal maintenance, as reflected in reduced ISG expression by d21. Alternatively, embryos with PL between d22 and 33 adequately signaled for luteal maintenance (ISG) but had delayed/inadequate embryonic attachment and/or inappropriate luteolysis causing PL.