ISG15 mRNA expressions in each pregnancy status of cattle after AI or ET. ISG15 mRNA expression (mean ± S.E.M.) on days 16, 18, 21, and 25 after standing estrus in pregnant, extended interestrous interval (≥ 25 d, eIEI), and normal interestrous interval (< 25 d, nIEI) cattle after AI (A) or ET (B). Data are presented as relative fold change from value on day 7; comparisons were made within each day. Different letters indicate a significant (P < 0.05) difference between values.