The objective of this study was to evaluate the trend of heterosis observed in monthly hen day rate of production and egg weight in F�1 crosses between the local and exotic layer type chicken. The heterosis observed for hen day rate of production were substantial and declined with age of lay in most of the crossbred groups. The heterosis observed for egg weight traits were mostly negative and non significant. The implication was that dominance variation decreased remarkably with age for egg production traits. 1316199583.php