The sustainable utilization of date palm leaves (DPL) and rice straw (RS) as feed materials for ruminant was evaluated using an in vitro wireless gas production technique.

Date palm leaves and RS were individually ensiled with lactic acid bacteria (LAB) for 45 d or used as substrates for the cultivation of Pleurotus ostreatus (PO) mushroom for 35 d. A total mixed ration was formulated as a control ration. In the other rations, berseem hay replaced DPL (ensiled without additives or ensiled with lactic acid bacteria or PO) at 25, 50, 75 and 100%. Ensiling with LAB did not affect the chemical composition of DPL or RS, while PO treatment reduced their fiber fractions contents. Ensiling without additives lowered (P<0.05) the asymptotic production of total gas, methane (CH4) and carbon dioxide (CO2), and the rate of CH4 and CO2 while increasing (P<0.05) the lag time of CH4 and CO2 production. Ensiling of materials with LAB and treatment with PO decreased (P<0.05) the asymptotic production of total gas, CH4 and CO2 production and decreased the rate of CH4 and CO2 production. Ensiling without additives decreased (P<0.05) total bacterial count, and increased (P<0.05) fermentation pH and total volatile fatty acids (VFA), while LAB ensiled DPL increased (P<0.05) total VFA and propionate concentrations and decreased total protozoal count. The PO treated DPL decreased (P<0.05) bacterial count, protozoal count and fermentation pH and increased total VFA production.

Replacing berseem hay with LAB or PO treated DPL at 25% increased gas production; however, increased CH4 and CO2 production, while the other replacement levels decreased total gas, CH4 and CO2 production. The treatment with LAB is more recommended than the PO treatment.