Ammonia and volatile fatty acids are significant sources of pollution. In wheat, xylans predominate as the primary non-starch polysaccharide while in barley β-glucan predominates. β-glucans have also been shown to support the growth of lactobacilli and bifidobacteria. By increasing bacterial activity in the hindgut, the pattern of nitrogen excretion and VFA production may be augmented. Exogenous enzymes may increase nutrient digestibility by degrading the β-glucan. It is hypothesised that the addition of an exogenous enzyme mix to a barley-based diet would result in a benefit in terms of increased nutrient digestibility however; this benefit may be reduced by an associated increase in ammonia emissions.