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The introduction of gilts into herds is a key element of management in commercial pig farms and this requires an efficient method for estrus synchronization of young animals. In this case the objective of this study was to evaluate the efficacy of Altrenogest treatment on reproductive performance of synchronized gilts in comparison with nonsynchronized animals depending of the age and the live weight of the animals. Two hundred sixty and two gilts were randomly assigned to two different groups: control group (55) and treated group (207) receiving 20 mg. of Altrenogest for 18 consecutive days. All animals were inseminated twice per estrus with semen dose of 80 ml. containing 3.0��109 spermatozoa. The conception rate and farrowing rate numerically increased in treated gilts in comparison to the control group ��� respectively with 7.46% and 7.72% (p>0.05). The same tendencies were found for litter parameters ��� 0.34 piglets more in total born and 0.39 piglets more born alive per litter. The age and the live weight of gilts had not statistically significant effect on their reproductive performance, but always the better reproductive performance was obtained in treated animals. The treatment with Altrenogestproved to be a highly effective method for managing the estrus in replacement gilts.