DNA testing not just for crime solving


SAN ANGELO, Texas – DNA identification is not only for crime solving and settling paternity suits.

It also has practical applications in animal agriculture, as researchers at the Texas A&M University System Agricultural Research and Extension Center are demonstrating.

Imagine. Imagine you are a registered sheep producer.

To properly register your animals, you must know for certain the parentage of each lamb.

How can you be sure which lamb or lambs belong to each ewe?

If the neighbor’s ram crawls through your pasture fence, how do you know which lambs are your ram’s?

Pairing the lambs visually with their mothers solves the maternity dilemma, though research has shown a 10 percent margin of error using this age-old method. That still doesn’t answer the paternity question.

Dan Waldron, Texas research geneticist, said there are only two sure ways of knowing “who belongs to whom.”

One way is to expose a given ewe or set of ewes to only one ram and closely observe the ewes at lambing time.

DNA. The second method is to use DNA testing.

Waldron and his peers started using DNA markers to determine parentage in a flock of Rambouillet ewes on the Center’s Barnhart Station in 2000.

A DNA marker is an identifiable trait within an animal’s genetic makeup.

Their study shows that with enough DNA markers producers can be 100 percent effective in determining a specific lamb’s dam and sire no matter how many rams are exposed to the ewes.

“We found DNA testing can save the conscientious purebred producer many headaches and often a good deal of money,” Waldron said.

“The labor, disease potential, feed costs and animal stress associated with pairing ewes and lambs the traditional way, that is, in a pen under close observation, is eliminated because the animals can be left out on pasture.”

The producer, he said, can register the animals when convenient, knowing the entries will be flawless.

The human error and frustration factors of pairing many lambs with their mothers are also avoided.

“Using DNA markers to determine paternity has another plus,” Waldron said. “It allows producers to use multiple sires on a group of ewes.

Pinpointing parentage. The technology can pinpoint any lamb’s parentage, even those from ewes having two or more lambs by different sires during the same pregnancy.

Being able to use multiple sires greatly reduces the chance of ewes not being bred due to fertility or health problems that might arise when using a single ram.

“DNA marker information can also be used to reveal incorrect pairings of ewes and lambs. It’s rare, but sometimes when many ewes are lambed in close confinement, a ewe may have one lamb and stop to have another. While she’s lambing again, another ewe almost ready to lamb may actually claim that first lamb for her own.”

Registered flock. In a registered purebred flock, Waldron explained, such an incident would be a pedigree inaccuracy unless the breeder caught the ewe in the act of stealing the lamb and noted the change.

He said all this can easily be avoided through DNA technology.

Waldron said breeders considering the use of DNA testing should brace themselves for a considerable initial cash outlay.

That’s because every breeding animal and all replacement animals entering the flock must be blood-sampled for DNA identification at a cost of about $25 per head.

Luckily, only one test derived from a single blood sample is needed for the life of the animal unless extra DNA markers are needed for perfect identification.

“It is expensive, but as more and more breeders start to use the technology, it should drop in price,” Waldron said.

“All things considered, though, the accuracy the technology offers and the headaches it alleviates should go a long way in helping beleaguered producers decide whether DNA testing is worth the price.”


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