Detection of Twins
| Early detection of twins is necessary to successfully manage the mare. Twinning is one of the main causes of abortion in the mare. Only 1-2% of twin pregnancies result in healthy foals so early reduction of one of the fetuses is an accepted management practice. |
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| Most twin pregnancies (98%) occur because multiple follicles ovulate during the cycle. There is a higher incidence in multiple ovulation in non-lactating mares older than 10 years. Breed and lines within a breed also play a role in the incidence of multiple ovulation. |
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Natural elimination of one fetus usually occurs before day 35 (85% of double ovulations). Most twin fetuses become fixed in one horn (70%) but only one vesicle/fetus continues to grow. Veterinarian intervention to terminate one of the twins should be attempted before fixation (day 12-16). The embryo to be terminated is forced via rectal palpation to the tip of one horm and then squeezed. Good survival of the other embryo does occur as 90% of the embryos not squeezed will survive. Abortion of a twin pregnancy can be done with prostaglandin (PGF2a) but should be done prior to day 35. This is the time at which the formation of the endometrial cups and production of eCG occurs. If PGF2a is given before day 35, the mare will more readily abort and cycle normally. |
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