Data of three upgrading trials of local Domiati cattle with Friesian (Friesian trial), Shorthorn (Shorthorn trial), or Jersey (Jersey trial), were used to quantify the importance of direct additive effect (G2), maternal additive effect (Gm), direct heterosis (I-it), maternal heterosis (H"), direct recombination loss (Fe) and maternal (R") recombination effect for some reproductive performance in these three up-grading trials conducted under hot climatic conditions. The reproductive performance used were age at first (AC 1) and second (AC2) calving and calving interval of all laclations (Cl). In the three upgrading trials , breed group effects were significant (P