The main objective in the present study was to determine whether reducing dietary CP level influences odour emission,
odour strength, odour offensiveness and ammonia emission from pig manure and fresh faeces and manure characteristics. In addition, the effects of reducing dietary CP on greenhouse gas concentration in the odorous air above the manure pit were also studied. It was found that reducing dietary crude protein from 15% to 12% in diets for finishing pigs did not reduce odour concentration, emission, hedonic tone and intensity from pig manure, although 9.5% ammonia emission reduction can be achieved for each % dietary CP reduction. The correlation between ammonia and odour emission is low, which means that strategies proved to reduce ammonia emission effectively may not have similar effects on odour emission. More dietary CP reduction may be required to reduce odour concentration and emission from pig manure. However, more odorous compounds in the manure and in the air should be analyzed in order to derive the relationship between dietary alterations and odour strength and offensiveness of the odorous air above the manure pit.

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