Crossbreeding remains one of the most effective low-input, high-return management practices a beef-cattle producer can adopt. Effective crossbreeding is more than just mating a bull and cow of different breeds. Crossbreeding systems with varying degrees of complexity offer benefits in proportion to the increased management they require.
Crossbreeding can increase production levels in two ways:
Crossbreeding provides the breeder the opportunity to combine the desirable characteristics of two or more breeds, thus achieving a higher overall performance level of desired traits. This is frequently called breed complementarity, which refers to the strong points of one breed complementing or covering up the weak points of the other breed.
Crossbreeding increases productivity for particular traits due to heterosis (also called hybrid vigor). The whole can be greater than the sum of the parts. For instance, if straightbred Hereford and Angus calves average 500 lbs. at weaning and Hereford x Angus calves average 525 lbs., the heterosis realized is (525-500)/500, or 5%.
The most commonly utilized crossbreeding systems in order from least to most demanding in terms of facilities and labor include:
- Two-breed cross,
- two-breed rotational cross,
- three-breed rotational cross,
- static terminal sire, and
- rotational terminal sire.
The ranking applies to the realized benefits. For instance, the two-breed cross is the easiest to manage, but results in the least heterosis and little opportunity for breed complementarity. Some crossbreeding systems offer a greater degree of heterosis than others, and some traits respond more to crossbreeding than others. Use of artificial insemination (AI) or multiple breeding pastures is required for use of complex systems.
Heterosis is realized in inverse proportion to heritability for a given trait. Lowly heritable traits offer the most heterosis; highly heritable traits offer the least. In general, reproductive traits are lowly heritable, growth traits are moderate and carcass traits are highly heritable.
Thus, differences in reproductive performance between herds are virtually all due to environment and management, while differences in growth or carcass traits are due primarily to genetics. Also, reproductive traits will respond the most to crossbreeding, carcass traits the least.
Before designing a crossbreeding system, the production environment and marketing goals must be determined. A balance of traits is usually best and little progress will be made by a breeder who tries to select for everything at once.
Clint Peck is director, Beef Quality Assurance, Montana State University.