Rick Bourdon

Colorado State University

"Composite" is one of the more popular buzz words in the beef cattle industry today. Cussed and discussed, composite cattle have been accused by some of adding to the industry's product inconsistency woes and touted by others as the solution to inconsistency problems. Composites are alternately considered a threat to and an opportunity for pure breeds. For all the controversy surrounding them, however, composites are little understood. My goal in this set of articles is to explain what composites are¾ perhaps clearing up some misconceptions along the way¾ and show why they can be useful to commercial cattle producers.

Composite individuals. Composite cattle, sometimes called synthetics, are hybrids. They have at least two breeds in their background and often more. What distinguishes them from typical crossbreds is not their genetic make-up per se, but rather the way in which they are used; composites are expected to be bred to their own kind, retaining a level of hybrid vigor we normally associate with traditional crossbreeding systems, but without crossbreeding.

For example, consider the standard black baldy cow. She is a hybrid, typically the result of mating a purebred Angus bull to a purebred Hereford cow or vice versa. In all likelihood she will be bred back to a purebred bull of one of the parent breeds or perhaps of a third breed. Because she is to be used as part of a conventional crossbreeding system, e.g., a rotation of some kind, we would not consider her a composite animal. However, if her owner decided to breed her to black baldy sires, saving daughters and perhaps even sons as replacements, we would have to consider her a composite. She became a composite (as opposed to simply a crossbred) because the breeder chose to mate her to her own hybrid kind with the expectation of retaining a degree of hybrid vigor without further crossbreeding.

Admittedly, this definition leaves a little to be desired. What if I have a herd of composite animals and one day I decide to breed them to terminal sires or make them part of a conventional rotational crossbreeding system? Are they still composite cows? Whether you answer yes or no depends on how strict you want to be in your definition of a composite. Being fairly liberal in this regard, I would say yes because these cows were bred to be part of a composite breeding system and still have that potential. Others may disagree.

Composite breeds. Most of our experience with composites comes from plants. Plant breeders developed composites as a practical way for farmers in third world countries to take advantage of hybrid vigor. The new plant populations were termed synthetic varieties. The analogous term in animal populations is composite breeds. In keeping with the definition of a composite animal, a composite breed is then a breed that is made up of two or more component breeds and is designed to benefit from hybrid vigor without crossing with other breeds.

There are a number of breeds in this country that are made up of component breeds. Brangus, Santa Gertrudis, Simbrah and RX3 are just a few examples. Whether these breeds have been bred in such a way that they retain significant hybrid vigor (i.e., whether they have successfully avoided inbreeding) remains an open question. If they have, then they can legitimately call themselves composite breeds. If they have not, then they are not composites, but simply newer breeds.

Perhaps the best way to answer this question is to compare the merits of a commercial breeding program involving composite cattle with the merits of more traditional systems. First, however, we need to decide how to make the comparison¾ to set the criteria by which any given system will be evaluated. Following is a list of the criteria I would use.

Merit of component breeds. For any crossbreeding system to be effective, the breeds in the system must be well chosen. If you were a horse breeder, for example, and were designing the ultimate crossbred stadium jumper, you would be unlikely to include the Shetland Pony as a component breed. Shetlands are simply too small to be viable candidates given the needs of stadium jumpers. The same principle applies to cattle. Every breed included in the system must bring favorable attributes to the mix. Because this is true regardless of the type of crossbreeding system, merit of component breeds is not a very useful criterion for comparing kinds of systems, and I will not, therefore, use it to compare the use of composites with other crossbreeding systems. It is an extremely important criterion, however, for evaluating any particular crossbreeding program.

Level of hybrid vigor produced (HV). One of the chief reasons for crossbreeding beef cattle is to take advantage of hybrid vigor or heterosis. Any worthwhile crossbreeding system must provide an adequate amount of hybrid vigor, and within the limits of practicality, the more hybrid vigor the better.

Simplicity (EASE). Crossbreeding systems should be relatively simple in terms of resource and management requirements. Expensive systems or systems that require an unrealistically high level of management are unlikely to remain in place very long.

Replacement considerations (REPS). Some crossbreeding systems produce the replacement females needed for the cow herd. Others require replacements to be purchased or bred in a separate population. Producers should evaluate both kinds of systems from the standpoint of economics and personal preference.

Complementarity (COMP). Complementarity refers to the production of a more desirable offspring from the mating of parents that are genetically different from each other, but have complementary attributes. The classic example in beef cattle is "big bull % small cow" complementarity. The big bull provides growth and leanness to the offspring, the small cow requires less feed to maintain herself, and the result is a desirable market animal economically produced. We can also have growth % milk complementarity and cutability % quality complementarity to list just a couple of examples. Unlike hybrid vigor, which is a sort of gene-level magic causing a boost in the performance of hybrids, complementarity is the logical result of "mixing and matching" different biological types. Some crossbreeding systems, terminal sire systems in particular, make good use of complementarity. Other systems do not.

Consistency of performance (CONS). Ideally, a crossbreeding system should produce a consistent product. It is much easier to market a uniform set of animals than a diverse one. It is also easier to manage a cow herd that is essentially one biological type than a herd made up of several types, each with different requirements. Crossbreeding systems vary in their ability to provide consistency.

Accuracy of genetic prediction (ACC). By now, most thoughtful commercial producers are sold on the idea of performance testing as a way of identifying genetically superior animals. Weights are O.K., trait ratios are better, and EPDs are even better predictors because they are more accurate¾ they are more likely to give us a true picture of an individual's genetic merit. Crossbreeding systems that use bulls with extensive EPD information allow more precise control over the genetic contribution of the sires.

Rick Bourdon

Colorado State University

In the previous article in this series, I defined composite cattle and developed a list of criteria for judging any crossbreeding system. The list is reproduced below. You can find a more detailed explanation of the list in the first article. My purpose in this second article is to evaluate composite breeding systems for the criteria in the list and in so doing give you a feeling for the relative strengths and weaknesses of composite cattle.

A basis for comparison: the traditional three-breed pasture rotation

To see how composite cattle stack up for these criteria, let's first establish a baseline by evaluating a better known traditional system¾ the three-breed pasture rotation. In this system there are three breeding pastures. Purebred bulls of three breeds are assigned to these pastures, one breed per pasture. Cows are allotted to pastures according to their breed composition¾ those with the least amount of a particular breed in their background are assigned to the pasture containing bulls of that breed. Replacement daughters, having different breed composition than their mothers, will be bred to a different sire breed. As shown in the accompanying figure, the entire scheme appears graphically as a rotation, with replacements moving sequentially from their dams' breeding pasture to the next breeding pasture in a circular fashion. 

Hybrid vigor, replacement considerations, and accuracy of genetic prediction. My evaluation of the three-breed rotation is summarized in the accompanying "report card." The system does well (scores a "+") in the hybrid vigor category. A large proportion of F1 or maximum achievable hybrid vigor, in theory 86%, is maintained with the rotation. The system also scores well in the replacement category because it produces all its own replacement females. Accuracy of genetic prediction is good too because the purebred bulls used are likely to come with state-of-the-art EPDs.

Simplicity. The three-breed rotation is not simple from a management standpoint, however. It requires at least three breeding pastures, and if heifers are bred separately from cows, an additional one to three pastures. Fencing, sorting animals, and keeping bulls in the right pastures can be painful. With cattle divided among a number of pastures, opportunities for high density/short duration grazing and related grazing schemes are limited. Furthermore, the system is infeasible for small herds¾ those using less than three bulls.

Complementarity and consistency. The three-breed rotation fairs poorly for complementarity and is questionable for consistency of performance. Because breed composition varies considerably within the herd (cows can be as much as 57% of a particular breed or as little as 14% of the same breed), the only way to be sure of consistent performance is to use breeds that are very similar in biological type. Doing so, however, rules out any possibility of breed complementarity. You could not, for example, use one breed that excels in milk production and another that excels in growth rate (a classic complementary combination) without producing sets of calves within a crop that differ a good deal in these traits. So if complementary breeds are used, consistency suffers, and if breeds are chosen for consistency, complementarity is eliminated.

Simplicity. Now consider the use of an existing composite breed. From a management standpoint, breeding composites is like breeding straightbreds; only one breeding pasture is needed (two if heifers are bred separately). All the problems associated with having multiple breeds are eliminated, and for this reason, the greatest virtue of a composite program may well be simplicity. Composites can be used successfully in small herds¾ even herds with only one sire, and with composites there should be no conflict between the breeding program and forage management. I give them a "++" in the EASE category.

Replacement considerations. Like straightbreds, composites produce their own female replacements, so composites score well for replacement considerations. Composites have the potential to produce their own replacement males as well, though for most commercial producers the extra level of management and record keeping required to do a good job of home-raised bull selection is probably impractical. Most composite bulls will be purchased from composite seedstock producers.

Hybrid vigor. Composite animals exhibit considerable hybrid vigor. For those of us schooled in the importance of crossbreeding for maintaining hybrid vigor, the idea of getting sustained vigor without crossbreeding may seem like voodoo genetics. In fact, it is an algebraic consequence of hybrid vigor theory. The amount of vigor depends on the number and proportions of component breeds in the composite. To get an idea of the fraction of maximum (F1) hybrid vigor that is maintained in advanced generations of a composite, you can use the following formula:

Proportion of F1 vigor retained = 78% ,

where pi is the proportion of the "ith" breed in a composite made up of n component breeds, and S is the mathematical symbol for summation.

The formula looks worse than it really is. Take the RX3 breed for example. RX3's are ¼ Hereford, ¼ Red Holstein, and ½ Red Angus. The fraction of maximum hybrid vigor retained in RX3's can be estimated as 63%.

In other words, RX3 cattle can be expected to exhibit 63% of the hybrid vigor typical of a first cross animal. A four-breed composite with equal fractions of each component breed would be expected to show 75% of F1 vigor, a similar eight-breed composite 88%. These are respectable amounts of hybrid vigor. Hence the "+" rating for composites in this category.

Breeders often ask, "After a while, won't a composite breed become just another breed?" In other words, won't composites lose their ability to retain hybrid vigor over time? The answer is no if inbreeding is avoided. On the other hand, if the composite breed is allowed to become inbred, as purebreds are, it will indeed become just another pure breed.

Consistency. Composites score high for consistency of performance. This comes as a surprise to many. Classical genetics texts are full of examples of increased variation in the progeny of hybrids. The books are not wrong, but the examples inevitably involve traits that are effected by just a few genes¾ so-called qualitative traits. In beef cattle, coat color is an example of a trait of this kind, and if the component breeds in a composite differ in color, the composites will be of many colors as well. The same is not true for quantitative traits¾ traits affected by many genes. These include the majority of economically important traits: fertility, survivability, growth rate, milk production, carcass characteristics, and so on. Experimental data suggest that composites are as uniform for these traits as purebreds. And when compared to hybrids from a rotational crossbreeding system, composites are inevitably more uniform because they do not vary in breed composition.

Complementarity. Does a composite breeding program make use of complementarity? Strictly speaking, no. Because the cattle within a composite population are all of the same basic biological type, there is little opportunity for complementarity from composite matings¾ no "big bull % small cow" possibilities. However, complementarity does come into play in the formation of composite breeds. We could, for example, include both Herefords and Holsteins in a composite to take advantage of their complementary characteristics. Note that this would be an unlikely pair of breeds to use in a rotational system using purebred sires; the fluctuation in offspring types would be too large.

Accuracy of genetic prediction. It is hard to say how composites will rate in the category of accuracy of genetic prediction. Currently, few composite bulls have EPDs and fewer have accurate EPDs. Purebred bulls have a big advantage here. This does not have to be the case, however. It is quite possible to calculate reliable EPDs for composites. What are needed are mechanisms for accumulating performance information on composites and the cooperation of purebred organizations in analyzing composite data.

Simply breeding composites to composites as though they were purebreds is not the only way to use composites commercially. A modified scheme (and, I confess, a favorite of mine) is the composite/terminal system. In this system, about half the herd of composite females, typically consisting of the heifers and younger cows, is bred to composite bulls, and the other half is bred to terminal sires (see the accompanying diagram). Replacement heifers come from the composite % composite matings, and all terminally sired offspring are marketed. Such a system involves an additional breeding pasture, but this modest loss in simplicity comes with an additional measure of complementarity (big bull % small cow) and hybrid vigor.

"Niche" cattle. As you can see from the "report card," composite cattle have a lot going for them and relatively few drawbacks. Composites have some additional attributes not readily apparent from the report card. They can be designed to fit a specific environment or niche. The Barzona breed is a good example. Barzonas were developed specifically for the desert southwest, and they combine characteristics from several breeds that make them particularly adapted to that environment. Wherever the environment poses unique challenges, there is an opportunity for an appropriately designed composite breed.

Reduced variation industry-wide. Composites have the potential for "standardizing" commercial cattle, thus reducing the variation we currently see in market animals. This statement may seem counterintuitive; how can variation be reduced by adding more breeds to the already large number of breeds available? Look at it this way. Today's problem cattle from a feedlot and carcass perspective tend to be biologically extreme animals. They are either purebreds or high percentage animals from extreme breeds or crosses of similarly extreme breeds. In other words, they are the result of poor crossbreeding decisions by commercial cattle breeders. With a composite breed, crossbreeding decisions are made when the breed is formed. Thus the decisions as to what breeds to put in the crossbred mix are taken out of the hands of commercial producers and placed in the hands of a much smaller number of composite seedstock breeders. Yes, commercial producers still decide what composite breed to use, but they are unlikely to find an extreme one. That is because (with rare exceptions) composites are expected to be complete and balanced in performance, and only those composite breeds that fulfill this expectation are likely to survive. In other words, the variation among composite breeds will be considerably less than the variation we now have among pure breeds.

Commercial or seedstock? Finally, composite cattle break the seedstock/commercial barrier. With traditional crossbreeding systems, crossbreds are the commercial cattle of choice due to their hybrid vigor, but only purebreds can be seedstock. Composites can be either or both. There is no genetic reason why a herd of good commercial composite cattle could not become a seedstock herd.