Odor is not new to dairy and livestock farming. Cows, pigs, and even sheep and chickens have always had special scents attached to them. But as farms get larger and non-farm neighbors move into the countryside, the smell of productive animals is no longer welcomed. Odor complaints often occur when manure is spread on the land. But odor and gaseous emissions are a daily occurrence wherever animals are housed or manure and feed are stored. Ammonia, hydrogen sulfide and methane (odorless) are emitted from storage lagoons, barns and feed storage areas as well as land where manure is applied. Though all of those areas can be a problem, you get the most for your money by evaluating and controlling emissions in manure storage areas. Efforts to control air emissions from manure can be divided into two categories: post-excretion strategies, which focus on reducing or changing emissions once manure has been excreted; and pre-excretion strategies, which focus on changing emissions prior to manure excretion. Post-excretion strategies are largely an engineering issue: treat manure or design a cover to trap emissions. These strategies may also be chemical, such as using manure additives to change the chemical properties of manure and, hence, the resulting emissions. Pre-excretion strategies are primarily dietary: change the composition of the diet (without changing animal performance) to change manure composition and, in turn, change air emissions. A pre-excretion approach can either reduce the nutrient precursors to emissions (source reduction) or change the form of the excretions. We do not know how diet strategies affect emissions once manure is moved into long-term storage. Theoretically, source reduction strategies should produce permanent results because they reduce the precursors to emissions, therefore, the maximum potential emission of a nutrient. On the other hand, form modification strategies may not produce a permanent result; ammonia that is not volatilized initially may be lost to the atmosphere during long-term storage because of adaptation of microbes or environmental changes. Most research has focused primarily on reducing ammonia emissions. Unfortunately, reducing ammonia may not reduce odor. Furthermore, the most commonly studied strategy has been to reduce nitrogen intake as a means of reducing nitrogen excretion and, ultimately, nitrogen emissions. To significantly reduce odor and gases in addition to ammonia, a combination of pre-excretion (source reduction plus form modification) strategies may produce more desirable results than one of the options alone. Diet modification strategies have demonstrated 40 percent or better reductions in ammonia emissions, and further benefits may be realized by adding on post-excretion strategies. The decision is complicated so you must consider all options and weigh the results against the desired outcomes.