A 2 × 2 factorial design Experiment 1 was conducted in order to characterize the effects of soyabean hulls (control or soyabean hulls diet) and metal-amino acid chelated minerals (MAC) (sulphate or MAC) on growth performance and nutrient digestibility in growing pigs. Forty eight pigs with the initial body weight (BW) 18.0 ± 1.1 kg were assigned on the basis of weight and sex to one of four treatments (2 pigs/pen, 6 replication pens/treatment, 6 barrows and 6 gilts/treatment). Throughout the experimental period, growth performance was not shown to be affected by dietary treatments. The coeffi cients of the total tract apparent digestibility of dry matter (DM) and nitrogen (N) remained unaffected by soyabean hulls diets or MAC supplementation. In Experiment 2, four barrows were used in a 4 × 4 Latin square design, to determine the effects of soyabean hulls and mineral types on emission of faeces and slurry noxious gas, including ammonia (NH 3 ), hydrogen sulphide (H 2 S) and mercaptans (R.SH), in growing pigs. Faeces and urine grab samples were collected, and the faeces (300 g) and slurry (faeces + urine = 150 + 150 g) were mixed, stored, and fermented for 5 d in order to evaluate noxious gas emission. Pigs fed diets with soyabean hulls tended to have lower NH 3 emission from faeces (P=0.09) than those fed the control diet, but NH 3 emission from the slurry was not affected by soyabean hulls diet (P=0.12). No signifi cant effects on the faeces or slurry NH 3 emission were exerted in MAC supplementation treatment. A signifi cant level of interaction between soyabean hulls and MAC was observed both in the faeces and slurry NH 3 emission (P=0.05, P=0.01). Pigs fed diets with soyabean hulls tend to exhibit lower H 2 S emission from the slurry (P=0.07), but signifi cantly lower levels of H 2 S emission both from faeces and slurry (P=0.004, P=0.02) was observed when pigs were fed on MAC diets. The emission of R.SH from faeces signifi cantly decreased (P=0.02) in MAC supplementation treatments, but not from slurry, and no soyabean hulls effects or interaction were observed in relation to R.SH emission.* Supported by the Rural Development Administration of Korea 1 Corresponding author: e-mail: inhokim@dankook.ac.kr Journal of Animal and Feed Sciences, 17, 2008, 171-181 SOYABEAN HULLS AND MAC IN GROWING PIGSWe conclude that the interaction between dietary soyabean hulls and MAC may have an effect on noxious gas emission. The emission of NH 3 from pig faeces could be substantially reduced by diets enriched with soyabean hulls and emission of H 2 S both from pig faeces and slurry could be reduced by MAC supplementation.