impact of genetic merit for milk somatic cell score of sires and maternal grandsires on herd life of their daughters a retrospective study of the impact of the estimated breeding values of sires and maternal grandsires for somatic cell score scs on productive life pl of holsteins and jerseys was conducted data included records from 2626425 holstein and 142725 jersey cows the sires and maternal grandsires of cows were required to have been available through artificial insemination and to have predicted transmitting ability pta scs evaluations based on 35 or more daughters a weighted function wpta of sire and maternal grandsire pta for scs was used sire pta 05 maternal grandsire pta15 the 3 dependent variables were pl frequency of cows culled for mastitis and firstlactation scs the model included effects of herd birth year and wpta wpta was categorized into groups or 330 for analysis of firstlactation scs calving year and calving month were substituted for birth year differences among wpta groups were highly significant as wpta increased pl decreased whereas percentage culled for mastitis and firstlactation scs increased the range in pl from lowest to highest wpta was 507 mo for holsteins and 473 mo for jerseys corresponding differences for percentage culled for mastitis were 70 and 56 and for scs were 095 and 104 for holsteins and jerseys respectively although phenotypic studies suggest that cows with extremely low scs were less resistant to mastitis our results showed consistent improvements in pl percentage culled for mastitis and scs of daughters when bulls were chosen for low pta scs