The present study reports the in vitro studies with furafylline and troleandomycin (TAO) as specific inhibitors of activities 7-methoxyresorufin-O-demethylase (MROD) and nifedipine oxidase, catalyzed by cytochrome P450 1A2 (CYP1A2) and 3A4 human enzymes, respectively, in hepatic microsomes of quail, duck,turkey and chicken. The results suggestthatin chicken and quailthe MROD activity is carried out by orthologs CYP1A4 and 1A5, meanwhile in duck and turkey by a CYP1A5 ortholog. The nifedipine oxidase activity is carried out by orthologs of the CYP3A family in the four bird species. The use of furafylline and TAO significantly decreased these activities (P < 0.05) and suggested that the biotransformation of resorufin methyl ether (RME) may be related to more than one avian ortholog.