Pregnancy rates and embryonic loss in Mangalarga Machador mares of different reproductive status used as recipients in programs of embryo transfer

The aim of this study was to evaluate the pregnancy rates and embryonic losses in Mangalarga Marchador mares of different reproductive status used as recipients in programs of embryo transfer (ET). Between the years 2004 and 2005 have been used 10 pluriparous mares as donors of embryos and as recipients, 21 nulliparous females, 20 pluriparous in lactation and 20 not lactating pluriparous. On The 8th day after ovulation were performed the embryos recovered of the donors and immediate transfer to the recipients. The diagnosis of pregnancy by ultrasound was conducted by the 7th day after the ET, repeating the tests on days 20, 25 and 30 of pregnancy. The total pregnancy diagnosed in the 7th day after ET and embryo loss in the 30th day of gestation was 67.21% (41/61) and 39.02% (16/41), respectively. With regard to the reproductive status, the rates of pregnancy and embryonic loss, did not show significant differences (P > 0.05). As for the age group, females with more than 11 years showed lower pregnancy rate (P < 0.05) than on the track between 6 and 8 years and between 9 and 11 years old and embryo loss had significantly higher (P < 0.05) than those in the lower range. With regard to gestational periods in which the embryonic losses occurred were not found significant differences (P > 0.05). Data obtained in this study suggests that Mangalarga Marchador mares regardless of reproductive status can be used successfully as recipients in programs for ET, but, is not recommended that females aged over 11 years are used for this function.