AbstractAn experiment was conducted to investigate the effect of dietary fermentable fibre on the pH and ammonia emission from slurry of growing-finishing pigs. Commercial crossbred barrows with initial body weight of 45 kg were used. Pigs were housed in two climate chambers. Twelve groups of 14 barrows were assigned to one of four diets. The diets differed in the content of fermentable fibre by adjusting the amount of sugar-beet pulp silage (SBPS). The control diet contained no SBPS. In the other three diets tapioca was replaced with three levels (50, 100 and 150 g/kg dry matter (DM)) of SBPS. After a 13-day adaptation period, the slurry was collected in a slurry channel for 7 days. A sample of this slurry was placed in a laboratory system to measure the pH and ammonia emission for a period of 7 days.The total volatile fatty acid (VTA) and DM concentration of the slurry increased as tapioca was replaced by SBPS. The ammonium concentration was not influenced by SBPS. For each 50 g/kg increase of SBPS, the pH of the slurry decreased by 0·45 units and ammonia emission decreased approximately by 0·15.It is concluded that increasing the level of fermentable fibre in the diet of growing-finishing pigs increases slurry VFA concentration. This consequently decreases the pH and ammonia emission from the slurry.