Rapid DNA Testing Progress Poses Major Challenges
27/07/06

Technologies that will deliver thousands of genetic tests on elite breeding animals at progressively more affordable prices are just around the corner, according to the latest international Genesis Faraday symposium. However, progress in high throughput genotyping is advancing faster than the animal breeding industry’s ability to understand and utilise the information, posing major challenges for all concerned.

“Livestock breeders are already using DNA tests to help the industry improve a growing number of important livestock traits, including meat quality in cattle and pigs, scrapie resistance in sheep and milk traits in dairy cattle,” explains Dr Alex Clop of Genesis Faraday. “They are proving really valuable. But as more and more tests become available it is an increasing challenge to ensure the test results are incorporated into breeding decision-making in the best possible way so they speed-up rather than compromise genetic progress.

“Understanding exactly what a particular DNA test shows and doesn’t show is vital in establishing breeding policy,” he stresses. “After all, a trait that is extremely valuable for a specialist sire line on the one hand can be equally undesirable in a dam line on the other.

“Equally, each genetic test needs to be given the proper weight in individual selection decisions or over-reliance on some traits can easily damage progress in others as well as severely reducing all-important genetic variation in the population. Furthermore, genes which impact some traits positively can have a negative effect on others. And the scale of the effect of most genes depends upon other genes in the population and interactions between them.

“Coping with this balancing act is difficult enough with one, five or even 10 separate DNA tests alongside existing measured traits. So you can imagine the scale of the challenge facing breeders as the number of tests grows rapidly.”

The Genesis Faraday symposium highlighted the progress being made by genetic researchers in establishing how best to combine DNA tests with conventional performance measures in improved selection indices. At the same time, however, it underlined how much work remains to be done to develop software able to effectively integrate large amounts of genetic test information into practical large-scale animal breeding tools.

“Thankfully, we have secured funds to start moving the development of such tools forward as a priority amongst our members,” Dr Clop reports. “For the immediate future, though, we urge all breeders to see DNA tests as a valuable addition to conventional performance testing rather than replacement for it. They should also be very wary of putting too much emphasis on any one trait or test in their breeding, keeping selection as balanced as possible unless there is a compelling reason not to do so, such as the National Scrapie Plan.”

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