Effect of cereal type and exogenous enzyme supplementation in pig diets on odour and ammonia emissions

A 2 × 2 factorial experiment was conducted to investigate the interaction between cereal type (wheat vs. barley) and exogenous enzyme supplementation (with or without) on odour concentration and ammonia emissions in grower–finisher pigs. The enzyme supplement used contained Endo-1, 3 (4)-β-glucanase (EC 3.2.1.6) and Endo-1, 4-β-xylanase (E.C 3.2.1.8). The diets were formulated to contain similar levels of digestible energy and lysine. The experimental treatments were as follows: (1) wheat-based diet, (2) wheat-based diet containing a β-glucanase and β-xylanase mixed enzyme supplement, (3) barley-based diet and (4) barley-based diet containing a β-glucanase and β-xylanase mixed enzyme supplement. The diets were offered to the pigs for 4 weeks and this was repeated 4 times (n = 4). Odour and ammonia emissions were measured on days 9, 11, 14, 16, 21 and 23 of each experimental period. Odour samples were collected in 20-litre Nalophan bags and analysed for odour concentration using an ECOMA Yes/No Olfactometer. Ammonia concentrations were measured using Dräger tubes. There was a cereal × enzyme interaction in odour emission rates (P < 0.05) and in ammonia emissions (P < 0.01). The addition of an enzyme supplement increased odour emissions and had no effect on ammonia emissions in the barley-based diet. The enzyme supplementation had no effect on odour but decreased ammonia emissions in the wheat based diet.