Volatile fatty acids in cattle supplemented with protein-enriched salt and sodium monensin

The effects of sodium monensin and protein supplements on volatile fatty acid production were studied in a 4 x 4 Latin Square design, using four female bovines equipped with rumen fistulae and fed Brachiaria brizantha Marandu cultivar hay. The treatments were organized in a 2 X 2 factorial array (with or without 160 mg of sodium monensin/animal/day and with or without protein supplements). Protein supplementation increased the concentration of acet ic acid and sodium monensin reduced the concentrati ons of acetic and butyric acids and the acetic : propri onic ratio, both with and without protein supplemen ts, except for the material collected at 8 h. Sodium mo nensin reduced the total concentration of fatty aci ds only in the material collected at 0 h, while protein sup plementation increased the concentration of fatty a cids at 4, 6 and 8 h. Used together, they increased the molar concentration of propionate in the rumen fluid, wit hout decreasing the total concentration of fatty acids.