High quality forage as a supplement to ruminants offered barley straw
Supplements of a high quality dried grass, urea and molasses, and sodium hydroxide (NaOH) treatment were used to improve the intake and dry matter digestibility (DMD) of straw. Grass depressed straw intake by lambs significantly but increased that by steers non-significantly. Grass provided extra crude protein and motabolisable energy to meet maintenance requirements, and promoted liveweight gain at high levels of supplementation. Urea increased straw intake by lambs significantly, and increased intake in steers when it was contained in the grass supplement rather than the straw. There was no interaction between urea and grass on straw intake. Molasses depressed intake and DMD by lambs of straw supplemented with urea, but slightly increased straw intake in steers. There was no interaction between grass and molasses. NaOH-treatment increased straw intake and DMD significantly. Urea improved the intake of NaOH-treated straw significantly but had no significant effect on DMD. NaOH-treated straw plus-urea promoted a similar intake to straw treated with urea alone, but DMD was significantly better for the former. Maximal straw intake by steers occurred when the diet contained 4.0-5.2g crude protein per MJ gross energy. This was interpreted as a suitable ratio for optimum cellulolysis.