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Livestock May Pollute Less with Feed AdditiveBy 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 USDAs 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 dont 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 wont 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.