Observed progeny performance validates the benefit of mating genetically elite beef sires to dairy females.

While several studies in cattle have confirmed the improved performance achievable from selection on total merit indexes, these studies have solely been confined to specific-purpose beef or dairy total merit indexes. Validation studies of total merit indexes used to select beef sires for use on dairy females are lacking. The objective here was to fill this void by quantifying the performance of beef × dairy progeny where the sire excels in either a total merit index encompassing calving performance and beef performance traits (dairy-beef index; DBI) or excels in a subindex based solely on calving performance (CLV); for comparative purposes, these beef × dairy progeny were also compared with dairy × dairy progeny. A total of 123,785 calving records from 101,773 dairy cows calving in 3,065 dairy herds were used; of these, 48,875 progeny also had carcass information. The beef sires were stratified into 5 equally sized groups based separately on their DBI or CLV. Linear and threshold mixed models were used to compare calving and carcass performance of all 3 sire genotypes. Of the 415 sires that ranked in the highest of the 5 strata on the CLV subindex, only 52% of them ranked in the highest stratum for the DBI. The percentage of primiparae requiring any assistance at calving was 2 to 3 percentage units greater for the higher DBI sires relative to both the higher CLV beef sires and the dairy sires (not ranked on anything); no difference existed in multiparae. The extent of calving difficulty in primiparae was, however, less in higher DBI beef sires relative to both the higher CLV beef sires and the dairy sires, although the differences were biologically small. Perinatal mortality was greatest in the beef sires relative to the dairy sires, but no difference existed between the high CLV or high DBI beef sires. No difference in progeny gestation length was evident between the high DBI or high CLV beef sires, although both were >2 d longer than progeny from dairy sires. The higher DBI sires produced progeny with heavier, more conformed carcasses relative to the progeny from both high CLV beef sires and dairy sires. No differences existed between the progeny of the beef sires ranked highly on the CLV versus those ranked highly on the DBI for the probability of achieving the specification for carcass weight (between 270 and 380 kg) or fat score; the higher DBI animals, however, had a 4 to 10% greater probability of achieving the minimum carcass conformation required. In all instances, the beef sires had a greater probability of achieving all specifications relative to the progeny from the dairy sires with the difference for conformation being particularly large. Results indicate that more balanced progeny can be generated using a DBI, helping meet the requirements of both dairy and beef producers. Ignoring market failure across sectors, using higher DBI sires could increase dairy herd profit by 3 to 5% over and above the status quo approach to selection in dairy (i.e., CLV subindex).