Weekly Genetics Review: Learn the difference between survey data and EBV as selection tools

Since the mid-1990s when ultrasound data became more commonly available, the number of animals scanned and presented with the data at sales, shows, and other events has become enormous.

On Angus Breed alone, a recent paper published in the American Zoological Society identified more than 640,000 animals that were scanned and registered in the Angus Australia database.

No doubt, scanning for the production traits of the oculomotor region, subcutaneous adiposity, and marbling has greatly improved the ability of producers to identify and select supergenes. The use of trained and certified scanners to record data and enter it into programs such as BreedPlan has been an important part of the continuous improvement in the accuracy of genetic information for animals in most breeds.

However, it is equally important to remember that ultrasound scan data must be considered and understood in context. Because the primary data collected is from the crush side, the available information only shows how animals measured at the same time, from a contemporaneous group, performed against each other.

While this data may sound impressive, the data collected cannot be compared against the breed average or even against other groups of animals operating in a different environment within a single property.

It is always important to keep in mind that an animal’s phenotype – its physical appearance – is a direct function of its genetic potential and the influence of its environment. An animal’s shape may not always accurately reflect the genetic potential of its offspring.

The raw data, either through scanning or simply weighing, is the range of the animal’s current phenotype. Until this data is used as part of a broader analysis, its use is limited to comparing similar animals at that location and at that time.

Carcase competition experience

After the recent slaughter competition, the risks of trying to use raw survey data as a predictor of offspring performance for a group of Queensland cattle producers were highlighted. The animals in question were bred by a bull which was listed in the sale catalog as having the largest EMA in the draft. However, his progeny was found when it was finally completed and sent to competition to be among the group with the smallest EMAs in competition.

While these are understandable reactions, they are incorrect on both accounts, and highlight the fact that many producers confuse raw data with EBV.

The almost immediate feedback was that somehow the cadaver data must have been wrong, as the animals had previously been fathered by an animal with a large EMA. The second reaction was to point out that the examination was wrong and inaccurate.

While these are understandable reactions, they are incorrect on both accounts, and highlight the fact that many producers confuse raw data with EBV.

It may have been true that the bull that fathered those animals had the largest EMA when scanned. However, all the survey data it shows is the result of the interaction between genetics and the environment for this bull. The assay data doesn’t really allow any insights into the genetic potential a bull had to alter for any offspring.

Much depends not only on the genes of the sire, but also on the genetics of the cows that the bull then joined. It is possible that the initial measurement was the largest in a group, but across a breed, when analyzed and compared to more data as part of the BreedPlan analysis, this was a one-off.

And in fact, the animal may be a genetic medium for this trait. It’s just that as an individual in that environment, Taurus was able to express greater EMA than his contemporaries.

Where this bull fits, either above, on par, or below average is the first half of the equation. Since the bull contributes half of the calf’s genes, the dam’s genetics is also a major factor in the final carcass outcome. If those cows are genetically average, or even below average, this has a direct impact on how much change a bull can make.

Finally, there is also the influence of the environment those calves were raised in prior to their entry into the carcass competition.

At the time, my message to breeders and producers is not to start blaming the wiper or the grade. Instead, the problem comes down to the information that was used to make that breeding decision.

Using raw scans for more than just looking at how animals grow and display traits in a given environment increases the risk that producers will select the wrong animals. Using this data, without knowing what needs to be corrected in a home breeding herd is a greater risk.

It is also worth remembering that cadaver competition data is also data that is effectively raw data from a single point in time. The results of one competition should not be seen as a signal to change the entire programme.

However, if the data can be combined with other data collected on the farm and from carcass feedback from commercial sales, a trend may start to emerge in areas where herds need improvement. If these attributes are corrected or improved, the most reliable indicator is the use of EBVs that have high accuracy. In the long run, this process is likely to be more effective in achieving the offspring outcomes that the program has in mind.

Alastair Rayner is Director of RaynerAg, an agricultural advisory service based in New South Wales. RaynerAg is a subsidiary of BJA Stock & station agents. He regularly lists and sells livestock to clients as well as attending bull sales to support clients’ purchases. Alastair provides pre-sale selections and grading to seed producers in NSW, Qld and Victoria. He can be contacted here or via his website at www.raynerag.com.au

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