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Multi-Breed Genetic Evaluation

Multi-breed genetic evaluation accounts for direct and maternal heterosis effects and breed effects, and it puts all animals in an evaluation such that additive genetic merit can be compared across all traits in the analysis.

Imagine being able to directly compare the genetic merit of seedstock, no matter what breed or breed combination. It would be the pinnacle of genetic-evaluation utility for commercial producers.

“As a producer, I'd like to have the whole world — both purebred and hybrid — from which to choose and compare bulls and AI sires,” says Kent Andersen, North American Limousin Foundation (NALF) executive vice president. “Multi-breed genetic evaluation is all about comparing animals of various breeds and breed combinations in a system whereby they can be compared directly to one another. It's about identifying the best animals across breed populations and composite populations for the purpose at hand.”

That's as opposed to the single-breed genetic evaluation that's been the staple of most breeds since modern beef cattle genetic evaluation began in the 1970s. Difference in genetic merit for specific traits is determined statistically via an animal's parentage, phenotypic performance, progeny performance and its relationship to others in the population.

Multi-breed analysis does the same thing, but with more accuracy by virtue of data volume. Plus, since animals of various populations are part of the genetic evaluation, every animal included can be compared directly with another. Without multi-breed analysis, the only way producers can get at comparing between breeds is with across-breed adjustment factors calculated by the U.S. Meat Animal Research Center. But those adjustments are limited to explaining breed differences and differences in base years (more later).

“Multi-breed genetic evaluation accounts for direct and maternal heterosis effects and breed effects, and it puts all animals in an evaluation such that additive genetic merit can be compared across all traits in the analysis,” Andersen explains.

Hybrids drive interest

This approach is less than revolutionary. The American Simmental Association (ASA) began multi-breed evaluation about a decade ago, says Wade Shafer, ASA director of performance programs.

Similarly, based on software and services from the University of Georgia, NALF and some others employ multi-breed analysis that includes EPDs from other breeds, which helps provide more reliable EPDs for registered hybrids.

Arguably, it's this growing use of registered hybrid and composite seedstock that's mostly fueled interest in multi-breed genetic evaluation during the past few years.

Shafer, who was a Simmental breeder when ASA adopted its multi-breed analysis, explains, “For Simmental, adopting multi-breed evaluation was largely brought about by a desire to better evaluate the many crossbred Simmental in our database that resulted from upgrading.”

Upgrading was primarily how Continental breeds introduced in the 1960s and '70s were developed in the U.S. Typically commercial cows were AI'd to fullblood semen resulting in a halfblood. That halfblood was mated to create a three-quarter blood and so on.

“The model we were using then wasn't really capable of evaluating upgraded cattle,” Shafer says. “Though the upgrading process has largely ceased, the dramatic increase in the development of composite seedstock has made ASA's multi-breed evaluation as relevant as ever.”

The ASA now provides multi-breed analysis for ASA, the Canadian Simmental Association, the American Chianina Association and the American Maine-Anjou Association. They began conducting the analysis in-house a year ago.

Another seed for increased interest has also grown from the National Beef Cattle Evaluation Consortium (NCBEC), whose members include the land-grant universities that have provided genetic evaluation. Long story short, these universities are shifting their resources away from running the analyses to research (see “Passing The EPD Torch,” page 48). Along the way, this group began to prototype how a single national genetic evaluation would look and work if all breeds were involved.

Dampened incentive

According to Craig Huffhines, American Hereford Association (AHA) executive vice president, part of that notion was that such an analysis would provide increased accuracy for the breeds involved, as well as more cost efficiency by working together.

“We didn't participate because there's minimal linkage between the Hereford database to other breeds, so there wouldn't be a more accurate comparison for our cattle. As for efficiency, we're extremely pleased with our current efficiency and cost,” Huffhines says.

In 2000, AHA moved its genetic evaluation to Australia, so they don't share others' wonderments about who in the U.S. will be providing service in the future.

Similarly, Robert Williams, American International Charolais Association (AICA) director of breed improvement, sees more benefit in breeds working together to provide genetic evaluation than necessarily conducting multi-breed evaluation together. The lack of relational connectivity to other breeds is part of it. That, and concerns about how doable it is with so many breeds involved.

“I think a producer first must decide which breeds fit his program, then pick the bulls from the breed that fits,” Williams says. “I believe multi-breed evaluations will be in our future. I'm just not sure we're at a point in the industry today to support widespread use of those evaluations.”

AICA has conducted a joint evaluation with the Canadian Charolais Association since 1998. “We still find a few animals not identified correctly. Across several breeds, those kinds of errors can increase exponentially,” Williams says.

Plus, Williams has concerns about turnaround time. “Collecting the records is one thing. Editing them (formatting them for analysis, finding duplicates, etc.) is another challenge.”

AICA is in discussions with other breeds about forming what it's dubbed the National Beef Center, a non-profit organization that would provide genetic evaluation services.

The American Angus Association (AAA), which represents the most common genetic glue in the industry, has yet to adopt multi-breed genetic evaluation for some of the same reasons, though they've created a new organization to provide these services.

“Our board created Angus Genetics, Inc. (AGI) as an entity to provide genetic-evaluation services for the industry. If other breeds are interested, we're making that service available to them,” says Bill Bowman, AAA's vice president of information and data programs.

“From a producer standpoint, the value of an evaluation that characterizes seedstock in a manner that can be directly comparable makes sense,” Bowman says. But he adds, “I don't think you'll see many breed associations switch to multi-breed analysis overnight if they haven't already been doing it.”

Change is never welcome

Aside from the unknowns of switching gears, reluctance stems from the heartburn that occurs when EPD numbers suddenly “look different.”

“Producers become familiar with what a certain EPD level means within a breed and within their herd, and then become understandably confused when that look changes,” Shafer says.

The best example of this usually revolves around changes in what's known as the base year for genetic evaluation. The current EPDs are reported based on their relationship to a base year; the average EPD value varies by year. Consequently, if breed Z were to adopt the base year of breed X for the sake of direct comparison, the weaning weight EPDs for breed Z might climb dramatically, but also its birthweight EPD. The bulls still rank the same in-breed and have the same genetic merit relative to one another, but the “look” of the numbers has changed significantly.

Shafer emphasizes that the science of genetic evaluation is mature enough — barring quantum leaps in research such as including genomic information (see “Fast-Forward Genetics,” page 38) — that the ranking of animals will likely remain fairly static between the evaluations offered by various organizations.

In the event the same animal is evaluated in more than one system and the animal's relative ranking is substantially different, Shafer reminds that EPD accuracy is the ace producers have up their sleeves to determine if one EPD is more meaningful for a particular animal than for another.

Especially in the new cattle industry defined by rising input costs, Andersen stresses multi-breed genetic evaluation provides more opportunity to more accurately manage genetic inputs.

“I think multi-breed analysis lends itself well to managing genetic inputs in multi-breed mating systems where the components that must be managed are additive genetic merit, breed complementarity and heterosis,” Andersen explains. “If you can compare the options directly, you can more easily swap different hybrids in and out, with the simplicity of straight-breeding and with more heterosis and more management of it. Right now, you're likely rotating purebreds in and out, so you're dealing with fluctuations in breed composition, or sticking to a single breed or hybrid and sacrificing some heterosis.”

As Shafer says, “It used to be that seedstock producers only needed to be familiar with the breed they produced. As with other meat animal species, modern cattle seedstock production will undoubtedly require utilizing an array of breeds and breed combinations. Multi-breed evaluation provides users a potent tool to accomplish that task.”

In sum, Andersen says, “From a technical standpoint, we have the ability to do multi-breed genetic evaluation. From a practical standpoint, as an industry, I think we're still mustering up the political will.”

TAGS: Breeding