In this study, the effects of using soy oil (SO), poultry fat (PF) and tallow (T) in broiler feed at fixed energy : protein ratio on field and slaughter parameters were evaluated. The average live weight (ALW), feed conversion ratio (FCR), production efficiency factor (PEF) and mortality were investigated as field performance parameters; carcass weight (CW), carcass yield (CY), heart–liver weight (HLW), heart–liver yield (HLY), abdominal fat weight (AFW) and abdominal fat yield (AFY) were investigated as slaughter performance parameters. The experiment was performed in accordance with animal welfare legislation of Turkey and continued for 41 d. It was conducted with a total of 12 600 Ross 308 broiler chicks from Ross 308 strain middle-aged (36 weeks) broiler breeders. Ten different diets in which SO in starter; SO, PF and T in grower and single; or equal mixing of them (SO PF, SO T, PF T) in finisher were used. When animal fat (PF and T) was used instead of SO, especially in grower feed, the field performance parameters improved except for mortality ( ). This situation was not seen in slaughter performance parameters except for CW, HLW and HLY ( ). However, it was found that sex affected slaughter performance parameters except for CY and AFW; higher CW and HLW and lower AFY and HLY were observed due to higher CW in male broilers ( ). In addition, the interactions between the type of the fat and sex were not found to be significant except for CW and CY ( ). At the end of the study, it was seen that if certain ratios are not exceeded, the use of animal fat instead of SO may be a good and economic alternative. Such an arrangement, which can be made depending on oil and fat prices, can reduce the feed cost, which is a more important result in terms of large integrations.