Implementing Crossbreeding Systems by Ryan Boldt, Director of Breed Improvement
When considering different management systems for commercial cattlemen, one of the most protable management decisions is to implement a crossbreeding system. A crossbreeding system is simply a mating system that looks to maximize hybrid vigor and breed complementarity. When considering implementing a crossbreeding system there are seven factors that need to be evaluated for implementing that system. These factors include the merit of the component breeds, hybrid vigor, breed complementarity, consistency in performance, replacement considerations, simplicity and accuracy of genetic predictions. Each of these factors have different effects in terms of the effectiveness of implementing each system and will be discussed in further detail in this article. Component Breeds The rst factor when looking at implementing a crossbreeding system is the merit of the component breeds. This is often the rst consideration when designing a crossbreeding program. This looks to identify breeds of animals where the mean breeding value of the animal will positively contribute to the objective of the crossbreeding system. Think for example, if your goal were to create a horse to win the Kentucky Derby through creating a crossbred horse. When considering breeds, the Shetland Pony would not make the list of breeds that would be considered. Hybrid Vigor The next factor in the evaluation is the level of hybrid vigor that would be achieved. Generally, the more hybrid vigor that can be achieved the better.
A crossbreeding system maximizes hybrid vigor and breed complemtarity.
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In all crossbreeding systems, the maximum hybrid vigor is experienced in the F1 mating of unrelated populations. From this point forward, the lower level of backcrossing to any breed previously used in the makeup of the parent animals will lead to a higher level of hybrid vigor in the resulting progeny. Elimination of backcrossing is not always easy or feasible. The system must be designed to maintain adequate levels of hybrid vigor but make it implementable. Breed Complementarity Breed complementarity is another important factor for crossbreeding systems and there are many different examples of this occurring in beef cattle breeding. A popular example would be using a terminal sire within a crossbreeding system to increase the terminal merit of offspring. In addition, there are examples where using different biological types of cattle are introduced to provide advantages of environment adaptability. Introduction of Bos Indicus animals into a cross is commonly done in environments where heat stress is a factor. Another way that breed complementarity can be achieved is through the use of hybrid seedstock. In this example, the breed complementarity part of the equation is achieved at the seedstock level. The different breeds are crossed to provide the desirable characteristics of each of the component breeds. These animals then can be used as parent animals in the system. Consistency of Performance After implementation of a crossbreeding system, consistency of performance in progeny becomes very important. It is common knowledge that groups of calves that are more similar are easier to market than those that are more diverse. This is also important on the cowherd side
