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"Whence Come Hog
(March 2000 AR magazine
Antimicrobial Compounds May Reduce Swine
Waste Odor By Ben
August 20, 2001
Service scientists have found that certain microbes, called gram- positive
anaerobic bacteria, often are responsible for offensive odors in stored swine
manure. Now the researchers are seeking a way to help better bacteria prevail
over the worst stinkers.
Gram-positive anaerobic bacteria are classified as such because
of their ability to retain particular stains or dyes. Examples of these
bacteria include clostridia, lactobacilli and streptococci.
At the National Center for
Agricultural Utilization Research, Peoria, Ill., microbiologist Michael A.
Cotta and his colleagues used classical microbiology and modern molecular
techniques to identify the predominant bacteria in slurries from hog manure
pits. The scientists work in the center's
Fermentation Biotechnology Research
Slurries rich in bacteria associated with methane and
foul-smelling compounds could become less offensive if hog producers treated
the pits with some as- yet-to-be identified effective antimicrobial compounds,
targeted against these bacteria.
To the scientists surprise, the commercial antimicrobial
compound, monensin, which inhibits growth of gram-positive bacteria in the
rumen of cows and other domestic animals to improve milk production or weight
gain, just didnt quite do the trick in laboratory research to reduce hog
manure odors. But the results did provide encouragement that the concept might
For their experiments, the scientists used samples of slurry of
manure from a swine barn pit, enriched with more hog feces. They found that, in
closed bottles, monensin quickly reduced methane and carbon dioxide production
and continued to do so for 28 days. And the total amount of volatile fatty
acids in the bottled samples decreased, at least slightly.
However, one of the foulest-smelling kind of fatty acids,
butyrate, increased 3-fold. So the search continues for an antimicrobial
compound that will inhibit the populations of butyrate-producing microbes.
ARS is the USDAs chief