The major advantage of crossbred dairy cattle is that they exhibit the strengths of all breeds from which they descend with an added advantage of heterosis. Heterosis tends to be most important for lowly heritable traits such as fertility and survival. The performance for a particular crossbred for a trait will be a combination of the breed merit for that trait of the breeds which make up the crossbred and the heterosis for that trait which is expressed in the crossbred. That combination can be higher than the breed merit for that trait of the superior breed in the crossbred’s makeup. The major disadvantages are that crossbreds also have the weaknesses of the breeds from which they descend and heterosis in initial crosses declines with any backcrossing to parental breeds.
Rotational crossbreeding plans, particularly with three breeds, can maintain substantial heterosis, but maintaining a rotational crossbreeding program requires careful record keeping and planning. One should be aware when crossbreeding that with early generations of crosses, there may be considerable diversity with regard to size, body condition, and other traits, depending on the breeds utilized. Benefits of crossbreeding depend on good sire selection within the pure breeds, just as purebreds depend on within-breed selection for genetic improvement.