Perda do concepto de éguas da raça Mangalarga marchador em diferentes status reprodutivos após a inseminação artificial e transferência de embriões

Abstract

Two studies were performed to evaluate in Mangalarga Marchador mares, the factors that influence the concepts loss after artificial insemination (AI), considering the group age, the reproductive status and the gestational period and the rates of pregnancy and embryonic loss of mares in different reproductive condition used as recipients in programs for embryo transfer (ET). In the first study, was performed between the years 2003 and 2006 were monitored the pregnancies of 320 mares, including nulliparous female (n = 52), not lactating pluriparous (n = 112) and pluriparous in lactation (n = 156) aged between 4 and 16 years. The diagnosis of pregnancy by ultrasound was conducted by the 15th day after ovulation, repeating the tests on the 20th, 30th and 45th day of pregnancy. The total of conceptus loss was 9.06% (29/320). Concerning the age group, losses of 8.06% (5/62), 6.58% (10/152) and 13.21% (14/106) for females under the age of 5, 5 to 10 years and 11 to 16 years respectively showed no significant differences (P > 0.05). Concerning the reproductive status, loss of 5.77% (3/52), 9.82% (11/112) and 9.61% (15/156) for females nulliparous, pluriparous non lactants and pluriparous in lactation, respectively, also showed no significant differences (P > 0.05). Considering the gestational period, the concept loss was more significant (P < 0.05) in the period from 15 to 20 days of gestation. Were not observed significant differences (P > 0.05)between the pregnancy rates loss of the mares inseminated in the foal heat 8.97% (7/78) and those inseminated in subsequent estrus 10.25% (8/78). Based on data from this study were unable to conclude that the reproductive status and age group did not influence the rates of theconcept loss, but, in the period between 2nd and 3rd week of gestation, the mares are more susceptible to these losses. In the second study, between the years 2004 and 2005 have been used pluriparous 10 mares as donors of embryos and 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 afterET 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 groups 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.