Dry matter intake (DMI), body weight gain (BWG), and feed conversion (FC) of steers fed combinations of calcium salts of isobutyric, isovaleric, 2-methylbutyric and valeric acids were measured at three trial sites. At each of two sites, 400 Hereford and Angus × Hereford steers averaging 292 kg in weight were randomly assigned to be fed, as percentages of the diet dry matter, 10 volatile fatty acid treatment mixtures. The experimental design, a 3 × 3 nested factorial arrangement of treatments, tested three levels of a mixture of isobutyric, isovaleric, 2-methylbutyric and valeric acids, three levels of a mixture of isobutyric, isovaleric and 2-methylbutyric acids, and three levels of a mixture of isobutyric and isovaleric acids. An unsupplemented control was also included. Combined data from the two trials demonstrated that DMI and BWG were not influenced by any treatment mixture. A 4.0% improvement ( P < 0.05) in FC over that of the control was observed in steers fed 0.20% of the four-acid mixture and 0.15% of the three-acid mixture, and a 3.2% improvement ( P < 0.10) in FC was observed in steers fed 0.28% of the three-acid mixture. Values for FC were 6.17, 5.92, 5.92 and 5.97 kg DMI kg −1 BWG for the control, four-acid, three-acid, and two-acid mixtures, respectively. At the third trial site, 336 steers averaging 257 kg in weight were randomly assigned to six volatile fatty acid treatment mixtures. The experimental design, a 2 × 2 nested factorial arrangement of treatments, tested two levels of the three-acid mixture and two levels of a mixture of isobutyric and 2-methylbutyric acids. An unsupplemented control and one level of the four-acid mixture were included in the test. A 5.3% improvement ( P < 0.005) in FC over that of the control was observed in steers fed 0.21% of the three-acid mixture. Values for FC were 5.69 and 5.39 kg DMI kg −1 BWG for the control and the three-acid treatment, respectively. In summary, feeding a mixture of isobutyric, isovaleric and 2-methylbutyric acids (0.40:0.34:0.26, anhydrous ratio) at a level not less than 0.15% and not more than 0.28% of the diet dry matter improved the FC of finishing steers. Including valeric acid in the mixture above did not further improve FC performance.