Reduced diet crude protein level, benzoic acid and inulin reduced ammonia, but failed to influence odour emission from finishing pigs

Intensified pig production is associated with odour and ammonia emissions causing nuisance and environmental concerns. The aim of four experiments was to investigate the effect of different dietary interventions on odour and ammonia emissions from finishing pigs. In exp. 1, diet crude protein levels of 16% and 14% were compared. In exps. 2 and 3, the effect of adding 1% and 3% benzoic acid, respectively, to the diets was studied. In exp. 4, inclusion of 15% inulin in the diet was investigated. All experiments were carried out in two identical climate chambers with three pens. There were 12 pigs per pen in total 36 pigs per chamber. Each dietary treatment was repeated two times. The temperature, ventilation rate and concentrations of NH₃ in the exhaust air were measured every hour. Odour concentration was measured in samples of the exhaust air by olfactometry. Reduced diet crude protein, the addition of 3% benzoic acid and inclusion of 15% inulin reduced ammonia emission by 30%, 57% and 34%, respectively. It was not possible to influence odour emission in any of the experiments.