The occurrence and outcome of multiple ovulation and pregnancy in the Thoroughbred mare

Abstract

Multiple pregnancies (MP) are almost always the result of multiple ovulations (MO) (Ginther and Bergfelt, 1988). Twinning is the most common non-infectious cause of abortion in the mare (Roberts and Myhre, 1983) and represents a significant economic loss. As a consequence, further investigation into its occurrence and outcome is warranted in order to determine effective management practices.Ultrasonic scanning was used to monitor and classify ovulation in 1582 Thoroughbred mares. Further ultrasonic scanning at Day 13 was used to identify and classify the resulting pregnancies (single pregnancy (SP), or MP)) in varying samples of mares. All MP mares underwent manual reduction of the smallest embryo at Day 13. 1170 mares, both SP and crushed MP, were monitored for the remainder of pregnancy with regard to pregnancy failure or success. Chi squared was used to test for significance throughout.