During the reproductiveseason of 2001 and 2002, 43 recipient mares of the Mangalarga Marchador breedwere treated randomly with intra-muscular application of 200mg/day of oily progesterone(P4). Another group of 41 mares of the same breed were treated randomly, viaoral, with 0.044 mg/kg/day of Altrenogest. Both treatments were performed betweenD0 (ovulation day) and D5. The recipients were evaluated on D2 and those inadequate conditions were in ovulated. Two groups of 85 mares of the same breedwere used as control by not receive any progestogen. They were also evaluatedand, when considered appropriate, in ovulated on D2 or D5. The groups D2/P4and D5 without progestogen presented a significantly greater percentage of recipientsconsidered appropriate during the evaluation, respectively 55 (64.71%) and 25(65.12%). In the group D2 with Altrenogest, 20 mares were considered appropriatefor in ovulation and 21 were not. The group D2 without progestogen showed asignificantly higher percentage of mares considered not appropriate. The pregnancyrate after in ovulation for the groups D2/P4 and D5 without progestogen wererespectively 72.72 and 76.36%, significantly higher than those from the othertreatments. The pregnancy rate for the group D2 with Altrenogest (52.38%) wasnot significant. Despite a larger number of non pregnant recipients for thegroup D2 without progestogen, it was not significant. The treatment of mareswith P4 from D0 to D5 indicates it is possible to anticipate the in ovulationof recipient mares to D2 and to obtain similar results to when in ovulated onD5.
