The influence of crude xylanase produced from Aspergillus niger FAS128 or FAS128 on the in vitro digestibility of pig diets and production performance of piglets was investigated in comparison with two commercial crude enzyme products, IE1 and IE2. The addition of FAS128 in all pig diets resulted in higher in vitro digestibility of dry matter (DM), crude fibre (CF), ether extract (EE), and ash than those supplemented with IE1 and IE2 (P<0.05). In 6-week feeding trials, weaned piglets fed with diets supplemented with FAS128 had a significantly higher average daily gain (ADG) and lower feed conversion ratio (FCR) than those given diets with IE1 and IE2 (P<0.05). The incidence of diarrhoea and concentration of blood urea nitrogen (BUN) of piglets at all growth period was also lowered. Based on the improved in vitro digestibility and production performance, crude xylanase produced from A. niger FAS128 has the potential for use as feed enzyme supplement. © 2007 Elsevier B.V. All rights reserved.