Aspergillus niger-fermented Ginkgo biloba leaves (FR) and its comparative effect with non-fermented G. biloba leaves (NF) were investigated on growth performance, small intestinal structure and function of broiler chicks. A total of 300 d-old Arbor Acress broilers were randomly allocated into 5 dietary treatments, which were then denoted as the control group (basal diet), and the NF group (containing 0.35% and 0.7% NF in the starter and grower diets, respectively), FR1. FR2 and FR3 groups containing 0.2%, 0.35% and 0.5% FR in the starter diets and 0.4%, 0.7% and 1.0% FR in the grower diets, respectively. The results showed that, compared with the control and NF groups, reduced (P < 0.05) feed/gain ratio of FR2 group and higher (P < 0.05) mucosal alkaline phosphatase (AKP) activities in duodenum and jejunum of groups FR2 and FR3 were observed. Villous height of duodenum and jejunum was improved (P < 0.05) as increased FR levels, while crypt depth of jejunum was decreased (P < 0.05). FR supplementation led to an increase in the protease activities in pancreas, duodenum and jejunum, as well as amylase activity in the duodenum and jejunum (P < 0.05 or P < 0.01, respectively). In addition, the sodium glucose co-transporter 1 (SGLT1) mRNA level in duodenum was increased in birds fed with FR2 and FR3 diets. Furthermore, birds supplemented with FRs had increased (P < 0.05) plasma D-xylose levels. Whereas compared with the control, broilers had lower (P < 0.05) serum urea nitrogen (SUN) levels when they were provided with the FR2 and FR3 diets. The present study may indicate that the improved feed efficiency and intestinal functions in the group supplemented with FR are directly connected with physiological mechanisms such as the regulation of the SGLT1 mRNA expression. (C) 2012 Elsevier B.V. All rights reserved.