抄録
This study aimed to predict pregnancy status within 21 d after AI by determining ISG-15 expression in peripheral blood leukocytes in dairy cows. Blood samples were collected from 31 lactating Holstein cows on d 0 (day of AI), 5, 12, 15-21 and 25; plasma progesterone (P4) levels were determined in 21 cows using EIA. ISG-15 mRNAs expression in leukocytes were determined in samples of d 12, 15-21 and 25 using semi-quantitative PCR. Pregnancy was diagnosed at around d 40 using transrectal ultrasonography. Cows were retrospectively divided into 3 groups: pregnant (n=10), showing estrus and/or low P4 between d 18 and 24 (Cyclic, n=13) and beyond d 24 (suspected embryonic death, SED, n=8). ISG-15 expression, as compared with respective values on d 12 in each group, increased on d 20 and 21 in pregnant cows (P<0.05), but not in cyclic and SED cows. When ISG-15 expression ≥ 1.25 (determined from ROC curve) on d 20 relative to d 12 was used to diagnose positive pregnancy, the sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were 90% (9/10), 95% (20/21), 90% (9/10) and 95% (20/21), respectively in all cows, and 87.5% (7/8), 100% (13/13), 7/7 (100%) and 93% (13/14) in 21 cows in which P4 was determined . When pregnancy was diagnosed by P4 > 1ng/ml on d 20, the sensitivity, specificity, PPV and NPV were 100% (8/8), 23% (3/13), 44.4% (8/18) and 100% (3/3), respectively. Thus, though ISG-15 expression may not predict the embryonic death, its expression on d 12 and 20 in peripheral blood leukocytes seems to be more effective than the P4 values for early pregnancy diagnosis in lactating Holstein cows.
