Study of early pregnancy factor (EPF) in equine (Equus caballus).

Problem: Early pregnancy factor (EPF) is an immunosuppressive protein detected in the early pregnancy serum. We have already reported that we developed the rosette inhibition test for mare EPF and detected EPF in thoroughbreds. The aim of this study was to determine whether or not our method could be used clinically.

Methods Of Study: The rosette inhibition test for equine EPF was carried out on serum from six nonpregnant and six pregnant Shetland ponies, a female and a male Chinese pony, and four nonpregnant and 13 pregnant thoroughbred mares. In the thoroughbreds sera were collected during the pregnancy period. Furthermore, we measured progesterone and detected pregnant mare serum gonadotrophin (PMSG) in order to confirm pregnancy of the Chinese pony 3 and 6 months after mating.

Results: In the nonpregnant Shetland ponies, the rosette inhibition titre (RIT) was 6.0+/-1.0 and EPF was negative. In contrast, in the pregnant ponies, the RIT was 9.2+/-0.4 and EPF was positive. Based on these results, we diagnosed pregnancy of the Chinese pony. The RIT of the female Chinese pony (3 months after mating) was above 10 and EPF was positive. Furthermore, we detected PMSG and progesterone in the serum of this pony. EPF appeared in the maternal blood circulation at 24-72 hr after mating, it was detected until the second trimester, and after that it disappeared from the maternal serum.

Conclusions: The pony's EPF was detected by using the same rosette inhibition test as in the thoroughbred and was present from 24 to 72 hr after mating until the second trimester. The results indicated that our method was useful for pregnancy diagnosis of Equine.