Performance of steers fed combinations of calcium salts of branched and unbranched fatty acids

Abstract

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.