It can't guarantee that the bull you buy will sire offspring that will achieve a particular USDA quality grade. But the GeneSTAR® marbling test — the world's first commercial diagnostic DNA test for a beef production trait — is proving to be a reliable tool seedstock producers can use to more accurately choose the level of marbling they want their cattle to pass along.

Specifically, Jay Hetzel, founder of Australia-based Genetic Solutions, Pty. Ltd., which developed GeneSTAR, explains the test identifies whether cattle carry two copies, one copy or no copies of the high-marbling form of the thyroglobulin gene. Hetzel says this gene explains about 10% of the genetic variation in marbling. While that may sound paltry, keep in mind research indicates that USDA quality grades account for less than that.

Added Prediction Increases Results

In tests so far, yearling-fed cattle with two copies of the thyroglobulin gene have produced 16% more Choice grade cattle than animals carrying one copy of the gene and 27% more than yearling-feds containing no copies of the gene.

Similarly, in research trials, calf-feds with two copies of the gene accounted for 12% more Choice grade carcasses than animals with one copy of the gene and 19% more than animals with no copies of it.

Plus, Hetzel says, “GeneSTAR's accuracy is relatively consistent across breeds.”

As one might suspect through experience and common sense, while consistent, the new test underscores the variation that exists between breeds and breed types (see Table 1 on page 46). Keep in mind, the breeds listed in the table represent only the relatively few cattle tested in the U.S. thus far. All told, about 3,000 GeneSTAR tests have been conducted on sires and dams from around the world.

With that said, Hetzel explains, “This is a particularly valuable test because it's what we call a direct test, and it can be used without knowing the animal's pedigree.

“Also, the results are quite simple. Producers don't need to know the magic in the laboratory, they just know that they can submit a sample of hair or semen from the animal and find out whether it contains one, two or no copies of the gene,” he adds.

How It Works

It really is that simple. Producers submit hair or semen samples to Genetic Solutions, which in turn gives the producer a report card that indicates whether the animal is carrying any copies of the high-marbling form of the gene and, if so, how many. The test costs $65-$80/head depending on the number of samples submitted for evaluation at one time. Producers can hold the results in confidence or make them public via Genetic Solution's Web site at

Again, the test only explains part of the puzzle. “It's only one of the genes associated with marbling, so it's only part of the marbling story in terms of genetics,” says Hetzel. “That will remain the case until other genes for marbling are identified.”

Consequently, an animal with no copies of the gene may indeed sire animals that can grade Choice and vice versa. In other words, the test does not replace Expected Progeny Differences (EPDs) for marbling and other tools of prediction, but it can increase selection accuracy.

“If we add gene marker information to performance data and pedigree information (current EPDs), we can build more accurate EPDs,” explains Jerry Lipsey, executive vice president of the American Simmental Association (ASA). ASA members have conducted the test on approximately 200 bulls and females. ASA is exploring the incorporation of this information into its national genetic evaluation.

So far, Lipsey says ASA members have used the test primarily to add marketing value to young bulls, help determine which bulls to retain for cleanup and to help identify donor females.

Bottom line, this particular test likely offers producers a glimpse of the type of selection tools they'll see more of in the future. Already, Genetic Solutions also offers another DNA test called SureTRAK, which some Australian beef packers are using to trace meat back to its original source.

“What the industry has been waiting for are tests for production traits that are difficult or expensive to measure in a conventional production system,” says Hetzel.

With GeneSTAR, it would appear the wait is over, at least when it comes to one gene that explains part of the variation in a trait the U.S. beef industry pays plenty of money for.