A feeding trial was conducted to estimate the optimum dietary protein and lipid levels for bullfrog(Rana catesbeiana).Twelve diets were formulated to contain three protein levels(35%,40% and 45%),each with four lipid levels(4%,7%,10% and 13%),in order to produce a range of P/E ratios(from 21.9 to 32.0 mg protein/kJ).The designed dietary protein and lipid levels in a brown fish meal-based formulation were achieved by serial adjustment of casein(for protein)or a mixture of fish oil and soybean oil(for lipid)at the expense of microcrystalline cellulose.Each diet was randomly assigned to three tanks(200 L),each tank was stocked with 12 bullfrogs[(91.5±0.10)g average initial body weight].Bullfrogs were fed twice daily(08:00 and 17:00)to apparent satiation for 8 weeks.The results showed that no significant differences in survival were found among all dietary treatments,but bullfrogs fed the diet with 13% lipid displayed liver lesions,such as abnormal color and crumbly texture.Weight gain(WG)and specific growth rate(SGR)of bullfrogs fed diet with 40% protein were significantly higher than those of bullfrogs fed diet with 35% protein(P<0.05),but there were no significant differences with bullfrogs fed diet with 45% protein(P>0.05).With increasing dietary protein levels,feed efficiency(FE)increased significantly,whereas,feed rate(FR)and protein efficiency ratio(PER)were just the opposite(P<0.05).WG,SGR and FR increased significantly with increasing dietary lipid levels(P<0.05),however,FE,PER and nitrogen retention were not significantly affected by dietary lipid levels(P>0.05).No significant difference was observed in body composition among all the groups at different dietary protein levels(P>0.05).Whole-body crude protein contents were not significantly affected by dietary lipid levels(P>0.05).However,whole-body crude lipid and energy contents increased significantly with increasing dietary lipid level(P<0.05).With increasing dietary lipid levels,hepatic malondialdehyde(MDA)concentration increased significantly,whereas,hepatic catalase(CAT)and lipoprotein lipase(LPL)activity were first increased and then decreased(P<0.05).The results of this study suggest that diet containing 40% protein and 7% lipid with a protein to energy ratio of 27.7 mg protein/kJ is optimal for bullfrog.