End of Project Report Summary The rationale for crossing dairy cows with beef bulls is to increase the beef productivity and value of the progeny. The proportion of dairy cows available for beef crossing is determined by the dairy herd replacement rate. The performance of cross-bred cattle is generally superior to the mean of the parent breeds because of heterosis. This is most pronounced for reproduction, maternal and calf survival traits. Crossing dairy cows with early maturing beef breeds (e.g. Angus, Hereford) has little effect on growth but improves carcass conformation and reduces feed intake. Crossing with most late maturing beef breeds also improves carcass conformation and reduces feed intake, but in addition, growth rate, kill-out proportion and carcass muscle proportion are increased. Cross breeding can have small negative effects on dam milk production, and subsequent reproduction can be impaired following a long gestation or difficult calving. There is little advantage in crossing with double muscled sire breeds (e.g. Belgian Blue, Piedmontese) compared with the larger conventional late maturing breeds (e.g. Charolais, Blonde d'Aquitaine). There are few effects of sire breed on meat quality.