In 1985, a project was designed and initiated at the SJBRC which sought to address several questions related to composite cattle crossbreeding. The focal point of the project has been to determine if crossing of phenotypically alike composite lines which differ in breed make-up will work to reduce variation yet produce high levels of heterosis.
Below is a excerpt from an article printed in the March 1991 Technical Report for the SJBRC.
COMPOSITE CROSSBREEDING PROJECT OUTLINE
San Juan Basin Research Center
D.W. Schafer, J.S. Brinks and A.H. Denham
The use of crossbreeding as a means of improving production has become widely accepted in today's commercial beef herds. However, conventional rotational crossbreeding schemes are often too cumbersome for very extensive operations or for smaller, one sire per year herds. Therefore, in efforts to maintain genetic diversity between sires and dams of comparable biological types and thus take advantage of heterosis, composite breeds have been developed.
Composite breeds have been developed in an attempt to combine complementing traits of two or more breeds into a single, superior biological type. By utilizing composite breeds, heterosis and breed complementarity can be maintained white producing uniform progeny in a simple "one breed" crossbreeding program.
Composite breeds have traditionally been developed for use in a particular environment. An example would be the Brahman influence in many of the breeds in the South. Matching a cow to her environment is an important consideration in breed selection for any crossbreeding program. Planning a comprehensive breeding program involves decisions relating to the number and types of breeds to be used with consideration given to Long term mating schedules and management of breeding pastures. To maximize breed complementarity, traits such as mature size, calving ease, milk production, survivability and fertility must be characterized for the chosen breeds.
A composite crossbreeding study was initiated in 1985 to evaluate two separate crossbreeding systems. In Phase I - System 1, MARC III, RX3 and CASH sires were mated to Hereford dams also in Phase I - System 2, Brangus, Barzona and Beefmaster sires were mated to Angus and Red Angus dams. In Phase II, crossbred heifers produced from each of the systems in Phase I were mated to one of the remaining two breeds in their respective system. In Phase III, progeny of Phase II will be systematically mated to incorporate the third composite thereby producing Phase IV progeny. Phase IV individuals will be mated inter se to form a new composite which will take advantage of heterosis and breed complementarity offered
Traits analyzed included birth weight (BW), calving ease (CE) actual weaning weight (WW), actual yearling weight (YW), pelvic height (PH), pelvic width (PW), pelvic area (PA), scrotal circumference (SC), hip height (HH), condition score (CS), reproductive tract score (RTS) and most probable producing ability (MPPA).
An objective of this study has been to select and mate composites with genetically diverse breeding but comparable biological type and form a new composite which utilizes the heterosis and breed complementarity offered by the three foundation composites. A second objective has been to evaluate the performance of the crossbred progeny produced in each of phases.