Herb oil may be the latest weapon in the battle against smelly and dangerous manure.
United States Department of Agriculture microbiologist Vincent H. Varel is using the essential oils carvacrol and thymol to block formation of foul-smelling volatile fatty acids in slurries of cattle feces and urine.
Varel has found that as little as one gram of the oils in one-half-litre slurry mixtures inhibits odor for weeks. Each was as effective as using the oils in combination.
Carvacrol and thymol are constituents of oregano oil. They can also be found in thyme and many other common herbal plants. Commercially, the compounds are synthetically produced and are oftenminor ingredients in foods and personal care products.
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Varel has also found that the oils can reduce E. coli in slurries.
USDA scientists are now moving their experiments from the laboratory to the feedlot to test the oils against potentially deadly bacteria E. coli O157:H7 and other pathogens.
The risk of meat contamination during slaughter increases when pathogen-laden manure sticks to the hides of cattle headed for slaughter.
Varel is also trying to find out if urease inhibitors can reduce feedlot ammonia emissions, which contribute to odors. One such inhibitor has been used as a nitrogen preservative in no-till cropping systems and is marketed for livestock waste treatments.
