8/8/97

Contacts:
Wendy Powers, Animal Science, (515) 294-1635
Brian Meyer, Agriculture Information, (515) 294-0706

BEWARE OF PRODUCT CLAIMS FOR DAIRY ODOR PROBLEMS

AMES, Iowa -- Dairy producers should be leery of products claiming to reduce odor from cow manure, says an Iowa State University researcher.

"We tested several commercial odor products on dairy manure and found no reduction in odor," said Wendy Powers, an assistant professor of animal science. She recently presented results of her work at the American Society of Animal Science annual meeting in Nashville, Tenn.

In southern states like Florida and Texas, odor from dairy and beef cattle operations has been as troublesome an issue as swine odor in the Midwest and other areas. "It's the same story around the country, but with different animals," Powers said. "More people are moving from urban to rural areas, and complaining about the smell from livestock operations."

Powers began the project while she was earning her doctorate at the University of Florida under the direction of Jack Van Horn. The project was funded by Florida dairy producers.

In laboratory tests, she studied the effectiveness of five commercial products on both fresh manure and treated manure. The treated manure underwent a process of anaerobic digestion, in which microbes break down organic matter into less odorous gases. The strength of odors was evaluated by trained panelists after one to three days &emdash; the average amount of time that Florida dairy producers store manure before applying it to cropland.

"We found no odor-reduction effects from the commercial products," Powers said. "Some decrease ammonia emissions, but there's no change in odor intensity. My advice for dairy producers is to be leery. If you do decide to use a product, make sure it's been tested under conditions similar to your own."

Although no odor reduction was associated with the products, Powers found that anaerobic digestion reduced odors up to 50 percent. "We believe producers can get benefits from simple digesters that contain something for bacteria to cling to. For example, putting wooden pallets into short-time storage facilities for liquid manure provides a surface for bacteria so they won't wash out when the liquid is removed. We need large microbe populations, and the pallets help them."

Another part of the project was determining whether chemical analysis can help predict odors. "We're not there yet," Powers said. "Odorous compounds react strongly with each other, so there could be concentrations of several compounds needed to predict odor. For now, the human nose is still the best odor measurement tool we have, even if it is the most biased."

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