Cluster analysisprinciples were used to allot bulls to be used as Multiple Service sires (MS).Expected Progeny Differences (EPDs) on pre- and postweaning traits were usedto calculate distances between bulls. EPDs were standardized and weighed toform a final selection index. The criteria to form lots was based on minimizingthe sum of all standardized distances for all possible pairs of bulls. The programwas tested on a set of 158 top bulls from a Nelore herd. A set of 4,740 breedingcows was used to evaluate three breeding strategies with the goal of producinggenetically superior individuals: (1) random mating; (2) single sire under designedmatings by a specific program (PAD); and (3) lots of multiple sires under designedmatings using PAD. Principal components was used to obtain the genetic biotypesexisting in these populations. Extreme values in EPDs amongst MS lots averagesand overall were very similar, indicating the program's ability to preservetotal variance. Variances of EPDs from calf crops obtained under the use ofPAD were increased three fold. Using designed matings by PAD allowed an increaseof 70% in the number of animals which would be recognized with official andfiscal benefits in comparison with random mating. First principal componentsfor cows, indicated that most genetic variability is accounted for preweaningtraits and visual scores at postweaning; the second indicated animals can becontrasted as good weaners and poor performer at yearling and vice-versa; thethird component showed diferences in sexual precocity. For single and multiplesires, despite the stronger selection pressure behind them, most of the remaininggenetic variability is associated with differences in precocity (traits associatedwith early finishing).
