MANAGEMENT OF TWIN PREGNANCY IN MARES

Twinning in mares is an ongoing problem. The equine uterus is usually unable to successfully carry viable twin fetuses to term. To accommoda te for double ovulation and twin conception, mares naturally reduce on e or both conceptuses by aborting one or both fetuses; abortion can oc cur as early as day 11 after ovulation or as late as 10 months of gest ation. In horses, twins nearly always result from multiple ovulations. factors that influence the tendency to ovulate more than one follicle include breed, reproductive status, and variation among individuals. Examination of the reproductive tract of a mare should be performed in light of the fact that any mare can ovulate multiple follicles. Equin e practitioners are increasingly successful in managing mares with twi n pregnancies as a result of advances in surgical techniques, the adve nt of ultrasonography, and the availability of effective nonsteroidal antiinflammatory drugs and progesterone analogues. This column summari zes the treatment options and su rates based on the stage at which twi ns are detected: day 14 to 16 after ovulation, day 17 to 34 after ovul ation, day 35 to 60 after ovulation, or day 61 to 170 after ovulation.