Crossbreeding has many different possible systems
Published on March 21, 2020
Increased heterosis in crossbred cattle is no secret in the beef community. In commercial herds, crossbreeding improves efficiency through heterosis and breed complementation.
University of Missouri (UM) Extension lays out the different systems and how they work.
“Crossbred cows with crossbred calves can be expected to wean as much as 25 percent more pounds of calf per cow exposed than purebred cows with purebred calves of the same average breed makeup,” UM explains. “To take advantage of breed complementation, breeds with good maternal ability and milk production would be used in a dam line and be mated to large framed, fast growing terminal sire breeds.”
“Optimal crossbreeding systems take advantage of individual and maternal heterosis and breed complementation,” UM explains. “An optimal system requires a minimum of three breeds.”
UM continues, “Unfortunately, it also requires multiple breeding pastures or artificial insemination (AI) to ensure correct matings resulting in maximum heterosis. A relatively large herd is required so that efficient use can be made of more than one breed of bull.”
However, UM notes there are ways for producers to reap the benefits of heterosis with a small herd and one to two bulls.
Specific crossbreeding systems
“Two-breed specific crossbreeding systems use a specific pattern of consistently mating a particular breed of bull to a particular breed or breed-cross of cow,” UM explains. “The resulting offspring are not brought back into the system.”
UM continues, “An example of a two-breed specific cross would be mating Angus bulls to Hereford cows. The resulting black baldy calves are sold. This system is used frequently in western range states.”
“Two-breed specific systems are often referred to as terminal systems because the progeny is not returned to the herd. This system provides maximum individual heterosis because the sire and dam have no common breed composition,” says UM. “No maternal heterosis is provided, since cows are purebred. Opportunity exists for breed complementation because maternal and paternal breeds can be chosen for favorable characteristics which contribute to the cross.”
“Most importantly, these breeds will be used consistently in their role as a maternal or paternal breed in this particular crossing system,” UM explains. “The source of replacement heifers is the major obstacle for using the two-breed specific crossbreeding system.”
“A three-breed specific or terminal cross results from mating Charolais bulls to the aforementioned black baldy cows. In the three-breed cross, both individual and maternal heterosis are maximized,” says UM.
“Maternal heterosis is maximized because the breeds crossed to produce the maternal line, the black baldies, have no common composition,” UM explains. “Individual heterosis is maximized because the maternal line, Angus and Hereford, has no common breed composition with the terminal sire, Charolais.”
“With this and all other specific crossbreeding systems, source of replacement heifers is a potential problem,” UM stresses. “A dependable supply is needed if they are to be purchased. Management considerations are important if the producer is to provide replacement heifers from within his own herd.”
“In a backcross system, heifers from a first cross are mated to a bull from one of the breeds in their own breed makeup,” says UM. “For example, a black baldy heifer might be mated to a Hereford bull. The backcross is most often used when a particular breed is well suited to the production environment such as indigenous breeds in tropical areas”
UM continues, “Backcrosses yield maximum maternal heterosis, but only 50 percent of maximum individual heterosis. The reduction in individual heterosis is due to the common breed makeup between bull and cow in the backcross.”
UM notes rotational systems involve a specific cyclical pattern on mating breeds of bulls to progeny resulting from a preceding cross. The simplest example of a rotational system is the two-breed rotation or criss-cross system.
“A series of alternating backcrosses are used in the two-breed rotation. In a Hereford-Angus rotation, progeny resulting from an initial Hereford-Angus cross would be backcrossed to one of the parental breeds, say Angus,” UM explains. “The resulting backcross progeny, three-quarters Angus and one-quarter Hereford, are mated to Hereford bulls.”
UM continues, “Progeny resulting from this third generation are mated to Angus bulls and this cyclical pattern continues.”
“Three-breed rotations simply add a third breed of bull to the cycle of matings used in a two-breed rotation,” UM notes. “Cows are mated to the breed of bull that makes up the smallest proportion of their own composition. A three-breed rotation increases use of individual and maternal heterosis to 86 percent of maximum.”
UM defines rotaterminal crosses as a combination of rotational and specific crossbreeding systems.
“They add some of the best features of each system,” UM boasts. “A rotation, usually of two maternal breeds, supplies cows for a terminal mating. For example, older cows from the Hereford-Angus two-breed rotation would be mated to bulls from a terminal sire breed.”
“Although not maximized in all the calves, some individual and maternal heterosis contributes to the performance of all calves produced. Approximately 40 to 60 percent of the cows are involved in the rotational part of the system,” says UM.
UM continues, “Individual and maternal heterosis is yielded by this part of the system at the same rate as that for a two-breed rotation. All male calves from this part of the system are sold while female calves are retained as needed for replacements.” “Crossbred cows from the maternal rotation are mated to a terminal sire breed. Cows express partial maternal heterosis and calves express 100 percent individual heterosis,” says UM.
Breed complementation is available from the terminal phase of the system. All calves from the terminal mating are sold.
“One advantage is that heifers usually are initially mated to a bull of similar size as their own sire breed as part of the rotation,” according to UM. “As cows mature and have a reduced likelihood of experiencing calving difficulty, they can be transferred to the terminal cross to be mated to a larger breed of bull.”
UM notes this system suffers the drawback of complexity and unequal usage of bulls. A minimum of four bulls must be utilized to properly operate the system, which makes it unattractive to the majority of beef producers.
Callie Hanson is the managing editor of the Wyoming Livestock Roundup. Send comments on this article to firstname.lastname@example.org.