Date of this Version
Nine measures related to breeding efficiency were used for comparisons among purebred Ayrshires, Brown Swiss, Holsteins, and Jerseys and between purebreds and 32 crossbred groups representing 2-breed, 3-breed, 5/8, and backcrosses by purebred sires and progeny of crossbred sires. There were four herds with Holsteins common to all, Brown Swiss and Jerseys in three herds and Ayrshires in one herd. Four 2-breed, two 3-breed, and two backcross groups were common to two or more herds. Among purebreds, breed effects were significant in 16 of 72 tests, but there was no consistent trend favoring one breed. Generally, Jerseys were better than Holsteins, and Brown Swiss were poorer than Holsteins. Purebred females bred to their breed required similar services for conception (1.77 versus 1.79) as when bred to a different breed of sire. Least squares estimates of differences between purebreds and crossbreds favored crossbreds in 86 of 144 tests suggesting advantages for breeding efficiency; however, few were significant. Standard errors frequently exceeded estimates of differences. Parity was not associated with superiority in the crosses.