The paper reports data from four experiments (EXP). The inclusion of 0.5% caprylic acid (CA) in diets reduced (P < 0.05) body weight (BW; EXP 1). The results of EXP 3 and 4 indicated that the diet supplemented with 0.25% CA and 30 mg vitamin E (total vitamin E concentration 50 mg) resulted in similar BW like the basal diet, but the increased supplemental vitamin E to 150 mg (EXP 3) or to 100 mg (EXP 4) decreased (P < 0.05 and P < 0.001) BW and increased mortality. Higher vitamin E doses in feed mixture significantly (P < 0.001) increased the content of vitamins soluble in fats in breast meat. The addition of caprylic acid significantly decreased the speed of lipid oxidation measured after 3 (P < 0.02) and 5 (P < 0.05) days of storage in refrigerator. On the contrary, higher vitamin E doses and basal diet without CA supplement increased the oxidation of lipids.