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Livestock May Pollute Less with
Feed Additive
By Jill Lee
December 3, 1996 NEW ORLEANS, Dec. 3--An
enzyme called phytase can be added to soybean meal feeds to reduce water
pollution around swine, poultry and fish farms, but the trick is making it
inexpensive to use, U.S. Department of
Agriculture scientists say.
“Experiments show phytase allows pigs, chickens and fish to digest the
phytic acid in soybean meal, converting it to the nutrient phosphate. Without
this enzyme all the phosphate in the phytic acid ends up in the animals’
waste,” said chemist Jaffor Ullah with USDA’s Agricultural Research
Service. “This high level of phosphate in animal waste then ends up
feeding polluting soil microorganisms or stream-choking algae. The phytic acid
in animal feeds also binds nutrients such as minerals and proteins so the
animals don’t benefit from them either.” Although phytase could
help some livestock make the most of their soybean meal, it is too expensive to
produce synthetically. And natural phytase degrades under the temperatures
required to make feed pellets, especially the heat needed to ensure fish meal
that won’t dissolve in ponds.
ARS geneticist Edward Mullaney hopes to solve two problems at once by
finding a desert fungus that naturally produces an inexpensive heat-tolerant
phytase. One promising candidate: a fungus called Aspergillus terreus.
Mullaney works with Ullah at the ARS Southern Regional Research Center in New
Orleans to find the genetic basis for heat stability.
“We have already identified several fungal genes that produce a more
heat-stable or highly active phytase,” said Mullaney. “To lower costs
further, we are also exploring whether genes coding for heat tolerant phytase
could be incorporated into soybean plants.” Phytase is now used
extensively in central Europe, where farmers pay a tax based on the amount of
phosphate their livestock release into the environment. In fact, these ARS
scientists have already helped other nations’ researchers develop the
potential of this commercial phytase feed additive.
Mullaney said that as more U.S. farms find themselves next to suburban
communities unaccustomed to animal waste odors, demand should increase for an
effective, yet inexpensive, way to include phytase in commercial feeds.
Scientific contact: Ed Mullaney or Jaffor Ullah, Environmental
Technology Research, Southern Regional Research Center, Agricultural Research
Service, USDA, New Orleans, La. 70179; phone (504) 286-4364, fax (504)
286-4419.
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