The term “composite” as used in beef cattle breeding refers to the mating of crossbred cattle that have the same breeds and fractions necessary to maintain heterosis and leverage breed complementarity. Two-breed animals are sometimes called hybrids and are typically 50 percent of each of the two breeds. Sometimes they may be 75 percent of one breed and 25 percent of the other. Common industry examples of composites are MARC II (25 percent each of Angus, Hereford, Simmental and Gelbvieh), Balancers (25 to 50 percent Gelbvieh and balance of breeding, either Red or Black Angus), LimFlex (Angus and Limousin hybrids), and SimAngus (Simmental and Red or Black Angus hybrid).
Hybrid or crossbred cattle can be produced by mating purebred bulls of one breed to purebred females of a second breed. Composites are generally produced by a continual crossbreeding system that utilizes crossbred females and crossbred bulls. Composites can be produced in a closed composite system, whereby no additional genetics is added, thus requiring a large population (more than 1,500 cows) to prevent inbreeding. A more common system of breeding composites is an open composite system that allows continual input of genetics from outside sources to prevent the buildup of inbreeding, thus eliminating the need for a large population and allowing the breeder to take advantage of outstanding bulls of various breeds or crossbreeds as they become proven.