Purdue animal scientist Alan Sutton has been looking at a method that may help reduce odor at the initial source -- the hog -- and would benefit both small and large producers. Sutton has been testing various modifications in swine diets in order to reduce odor and the potential for water pollution, while maintaining the animals' feed efficiency.
The study identified the predominant compounds that cause odor in manure, most of which are ammonia, sulfide compounds from amino acid digestion and volatile organic compounds. The researcher went on to evaluate changes in the odor-causing substances as a result of four diets: deficient protein diet; standard protein diet; amino acid balanced diet; and excess protein diet.
Based on initial results, reducing the crude protein level of the pig's diet and supplementing with essential amino acids reduced nitrogen excretion by 20 percent to 42 percent and dropped ammonia concentrations by 25 percent to 42 percent. Direct measurement of aerial ammonia over anaerobically stored manure showed up to a 64 percent reduction in odor-causing compounds. Not only is odor controlled, the diet also limits the amount of some compounds that could affect water quality.
Sutton was co-chairman of a Council for Agricultural Science and Technology task force report on Integrated Animal Waste Management. The report raises concerns that smaller hog farmers will be unable to afford or unwilling to invest in odor-control technologies that do not add to farm profitability. Still, he says he believes that all hog farms will have to get a handle on odor control, citing an increase in the number of odor-related lawsuits and public objections to opening new facilities and expanding existing ones.
"Odor is size-neutral," Sutton says. "It won't matter if you're a factory farm or a family operation if you can't keep the smell away from your neighbors."
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