IN-VITRO DIGESTIBILITY OF BARLEY AND WHEAT STRAWS TREATED WITH HYDROGEN-PEROXIDE, SODIUM-HYDROXIDE AND SODIUM PEROXIDE UNDER VARIOUS CONDITIONS

Five factorial experiments were conducted to evaluate the use of different amounts (0-600 g kg(-1)) of hydrogen peroxide (H2O2) in improving the in vitro digestibility of barley and wheat straws under different pH (5.6, 11.5), storage times (2, 7, 14, 21, 28 days) and straw/liquid ratios (8:1, 4:1, 2:1, 1:1, 1:6). The use of NaOH (50 g kg(-1) straw at 8:1, 4:1 and 1:1 ratios) and Na2O2 (15 and 45 g kg(-1) straw at 1:1 ratio) was also tested. In vitro digestibility of untreated (UBS) and ammonia-treated barley straw increased linearly (Experiment 1) with increase in H2O2 at pH 11.5 (alkaline H2O2, AHP). In Experiment 2, however, the digestibility of UBS increased curvilinearly (P < 0.001) with increase in AHP. In contrast digestibility decreased curvilinearly (P < 0.001) when H2O2 was applied at pH 5.6 (Experiment 2). In vitro digestibility increased with AHP in a dose related manner at different storage times (Experiments 3 and 4). In vitro digestibility of wheat straw was also increased (P < 0.001) with AHP treatments. However, the effect was not as great as with Na2O2 (45 g kg(-1)) or NaOH (50 g kg(-1)) when compared at same ratios of 1:1 (Experiment 5), NaOH being the most effective (P < 0.001) in improving digestibility. The full potential of AHP was perhaps masked by inhibitory soluble products released from straws which may have hampered the in vitro microbial digestion. Further studies are suggested to exploit the full potential of AHP.