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Tarbush spectra

Laser Illuminates Livestock Menus on the Range

By Don Comis
August 7, 1998

Roaming the range with a laser aimed at livestock droppings could allow instant analysis of a cow or sheep's diet. An animal with peculiar tastes for a weed could be a potential sire of generations of "designer mowers."

That's Dean M. Anderson's vision. He's an Agricultural Research Service animal researcher at the 193,000-acre Jornada Experimental Range near Las Cruces, New Mexico. The vision came from a test in a darkened physics lab at New Mexico State University when laser bursts were fired at a sheep pellet mounted on a pin.

The laser excited the pellet's electrons, generating a telltale pattern of light wavelengths on the screen of a computer connected to the laser. Linking this image to chemicals found in plants reveals an animal's diet. Then, researchers might better advise ranchers on how to match grazing animals to their lands. For example, if sheep crave a certain weed that goats won't eat, it would make sense to recommend sheep on land with that plant.

Anderson has teamed up with scientists at Sandia National Laboratory in Albuquerque to test the technique with xenon lamps and other alternatives to laser light that are more readily available and less destructive.

They have analyzed more than 100 samples of plants and manure and found light fingerprints of many plants including alfalfa. The U.S. Bureau of Land Management plans to help fund the research this year.

The technique has possible applications for monitoring the diets of wildlife as well.

An article on the light experiments appears in the August issue of ARS' Agricultural Research magazine. The article also is on the World Wide Web at:


Scientific Contacts: Dean M. Anderson, Jornada Experimental Range, Las Cruces, New Mexico, phone (505) 646-5190, fax (505) 646-5889,

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