Moser defined a mating system as the choice of breeds used, and the manner in which they are used as parents in a breeding program. Sire selection, he said, is picking the individual bulls to use within that mating system. Heterosis, sometimes called hybrid vigor, is the performance change observed in cross-bred animals which is above the average of the breeds involved.
Direct heterosis is the boost from cross-breeding, seen in the calf.
Maternal heterosis is the improvement in production resulting from a cross-bred dam. Fertility, milk production and growth improve slowly through selection, Moser added, but are quickly affected by heterosis. A four-breed cross can create significant genetic variation within a herd . Uniformity should be the goal, Moser said. Correct choice of breeds is important.