MONITORING BOVINE EMBRYO VIABILITY WITH EARLY-PREGNANCY FACTOR

The viability of the bovine embryo was monitored by measuring the earl y pregnancy factor (EPF). The EPF activity was measured by the rosette inhibition test before and after artificial insemination (AI) at natu ral estrus (n = 14), and after superovulatory treatment followed by em bryo removal on day 7 after AI (n=5). In the cows inseminated artifici ally at natural estrus, there were significant differences (p<0.01) in the rosette inhibition titer (RIT) between pregnant and non-pregnant cows on day 13-16 and day 20-25 after AI. In the 8 pregnant cows, the RIT remained more than 5 from day 6-9 after AI. In the 6 non-pregnant cows, two patterns were observed. In one pattern, RIT rose transiently to more than 5 and decreased to less than 4 thereafter. In the other pattern, RIT remained less than 4 throughout the experimental period. The former pattern suggested early embryonic death, while the latter s uggested that fertilization had not taken place or that early embryoni c death had occurred before the first blood collection on day 6-9 afte r AI. In the cows superovulated followed by embryo removal on day 7 af ter Al, the RIT values were all less than 4 on the day of AI (day 0), rose to more than 5 on day 3 and thereafter then until the day of embr yo removal on day 7. In 4 cows, the RIT decreased to less than 4 by 3 days after embryo removal, and in the remaining one cow, the RIT decre ased to less than 4 by 7 days after embryo removal. These findings sug gest that the measurement of EPF activity is useful for monitoring the viability of bovine embryos.