Effect of Molasses Level on Digestibility of a High Concentrate Ration and on Molar Proportions of Volatile Fatty Acids Produced in the Rumen of Dairy Steers

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Abstract
A high-concentrate ration containing molasses at levels of 0, 6, 12, and 18% of the concentrate portion was fed to 4 rumen-fistulated steers in a 4 x 4 Latin square balanced for carryover effects. The digestibilities of dry matter, cellulose, and energy were 75.2, 68.4, and 75.4%, respectively, for the control ration with no molasses, and averaged 68.7, 59.9, and 68.5% respectively for the molasses-containing rations. These were significantly different. There were no detected differences among levels of molasses. The average digestibility of crude protein for all rations was 73.4% and no significant differences among rations were found. Molar proportions of isovaleric acid were 2.72, 258, 2.27, and 2.38% for the 0, 6, 12, and 18% molasses rations. There was a significant difference between the control ration with no molasses, which was higher, and the rations with molasses, but no differences among the molasses-containing rations were detected. The average molar proportions of acetic, propionic, butyric, and valeric acids were 63.1, 19.9, 13.0, and 1.6%, respectively, and were not altered by the level of molasses in the diet. Isobutyric and 2-methylbutyric were included in the butyric and isovaleric acid fractions, respectively. Average pH of the rumen contents was 6.60 and was not significantly different for the experimental rations. At levels up to 18% molasses, some rumen functions were significantly but not greatly altered.