1. A study was carried out to evaluate the expression of growth hormone (GH), insulin-like growth factor I (IGF-I), mitochondrial adenine nucleotide translocase (ANT), cytochrome oxidase III (COX III) and avian uncoupling protein (avUCP) genes in 14-d-old Japanese quail that were fed different levels of glycerol (0%, 4%, and 12% dietary glycerol) which replaced maize as an energy source. 2. Total RNA was extracted from the breast muscle, and cDNA was amplified using real-time PCR with primers specific to the examined genes. 3. Quail fed the diet with 12% glycerol supplementation presented higher growth hormone (GH) mRNA expression than did those fed 0% glycerol. Supplementation with 12% glycerol negatively influenced IGF-I mRNA expression and reduced ANT mRNA expression in comparison with the treatment with no glycerol. COX III mRNA expression in the pectoralis superficialis muscle was decreased by 26% in quail fed 12% glycerol compared with those fed 0 and 4% glycerol. 4. There was no difference in UCP mRNA expression between quail fed 0 and 4% glycerol; however, UCP expression was reduced (73%) in birds fed the 12% glycerol diet compared with the level in those fed the 4% glycerol diet. 5. The inclusion of 4% glycerol in the diet produced results similar to those of the diet with no glycerol. Based on quail performance and the expression of the GH, IGF-I, ANT, COX III and UCP genes, 4% glycerol can be used in quail feeding without any harmful effects.