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Countless Microbes in Hog Manure Await Identification / March 3, 2000 / News from the USDA Agricultural Research Service

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Microbiologist Terry Whitehead collects fresh manure samples for use in tests.

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Countless Microbes in Hog Manure Await Identification

By Ben Hardin
March 3, 2000

Getting “down and dirty” may be the best way to figure out which microbes are causing the offensive odors that plague hog manure pits. Agricultural Research Service scientists are taking that approach to sort out the microbes that produce offensive smells from those that produce methane, an odorless “greenhouse-effect” gas.

In mid-1999, ARS scientists at the National Center for Agricultural Utilization Research began dipping into hog manure pits. When examining these samples, they found a rich assortment of microbes. The researchers are seeking to know them by their DNA--a unique genetic profile--as well as by classical biochemical features. So far they’ve deciphered more than 100 DNA sequences from 180 pure cultures in a group of microbes called eubacteria.

What the scientists most want to know is which eubacteria are the real stinkers--and what causes their numbers to rise or fall. That would be a fundamental step toward helping the livestock industry live in harmony with rural and urban neighbors. And reducing odors might go hand-in-hand with improving pork production efficiency because odors are produced mainly from feed that’s not fully digested.

The scientists ferreted out about 100 microbial DNA sequences directly from materials such as slurries of manure. These sequences included those from at least seven groups of methane- producing microbes of a type called archaebacteria. Only about half the groups have relatives in genera known to science. Archaebacteria live where there is little or no oxygen.

As the NCAUR scientists identify microbes that produce certain odors most abundantly, they will compare their data with findings from ARS colleagues at Ames, Iowa, who are analyzing odors from air samples near livestock operations. Although the NCAUR scientists are focusing on the pit storage environment, what they learn may be applied to research on manure that is composted or processed through lagoons.

ARS is the USDA’s chief scientific agency.

An article about the research appears in the March issue of Agricultural Research magazine.

Scientific contact: Michael A. Cotta and Terence R. Whitehead, ARS National Center for Agricultural Utilization Research, Peoria, Ill., phone (309) 681-6567, fax (309) 681-6686, and

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