MEASUREMENT OF EARLY-PREGNANCY FACTOR ACTIVITY FOR MONITORING THE VIABILITY OF THE EQUINE EMBRYO

The viability of embryos before flushing from donor mares (n=5) and af ter transfer to recipient mares (n=7) was monitored in mare serum by d etecting early pregnancy factor (EPF) using the rosette inhibition tes t (RIT). The EPF activity was measured in donor mares before and after natural mating at natural estrus; after ovulation on Days 2, 5 and 8; and after embryo flushing (Day 8) on Days 8, 9, 10 and 13 after ovula tion. The collected embryos were transferred immediately after flushin g. The EPF activity in recipient mares were measured on the day of tra nsfer and after embryo transfer on Days 1, 2, 3 and 5. Pregnancy was c onfirmed on Day 12 to 14 after embryo transfer. The mean EPF activity of donor mares was increased to the pregnant level (> an RI titer scor e of 10) on Day 2 after ovulation. Two days after flushing the embryos , the EPF activity of donor mares had decreased to the nonpregnant lev el. Among the 7 recipient mares, 3 mares were diagnosed pregnant on Da y 12 after embryo transfer with ultrasound. The EPF activity of the pr egnant recipient mares was increased above the minimum level observed in pregnant mares on Days 2 to 3 after transfer. However, among the no npregnant recipient mares after embryo transfer, the EPF activity of 3 mares remained at the pregnant level only 2 to 3 d and then declined to the nonpregnant level. In one recipient mare, EPF activity did not reach the pregnant level throughout the sample collection. The results of this study indicated that equine EPF can be detected in serum of p regnant mares as early as Day 2 after ovulation. From our observation, we conclude that the measurement of EPF activity is useful for monito ring the in vivo viability of equine embryos and early detection of em bryonic death. (C) 1998 by Elsevier Science Inc.