The aim of this study was to determine the chemical composition of stem and compost of the button mushroom to estimate metabolizable energy (ME) and net energy of lactation (NEl) using gas production method and to determine the amount of dry matter disappearance (DMD) using in vitro technique. This study was conducted in a completely randomized design with three treatments of mushroom stem, alfalfa, and compost. The data were analyzed by SAS software. Dry matter (DM), crude protein (CP), crude ash (CA), ether extract (EE), acid detergent fiber (ADF) and neutral detergent fiber (NDF) content of the stem, compost and alfalfa were: 10.3, 16.8, 8.6, 3.48, 31.5, and 13.4; 42.4, 12.8, 42.41, 3.14, 21.5, and 16.2; 96.4, 12.6, 9, 2.2, 38.6, and 32.3, respectively. The highest and the lowest amounts of gas production after 120 h of incubation were obtained for mushroom stem and compost, respectively. Gas production potential (a+b) of mushroom stem, alfalfa, and compost were obtained as 223.01, 200.0, and 114.53 mL gas/g DM, respectively. Gas production rates for mushroom stem, compost, and alfalfa were 0.07, 0.03, and 0.08/h, respectively. The highest values of ME and NEl were received for mushroom stem (8.01 and 4.82 MJ/kg DM, respectively). DMD was higher and lower in the mushroom stem and compost, respectively. The results demonstrated that mushroom stem had a higher nutritive value compared with the other experiment feeds and can be used in ruminant ration formulation. تفاصيل المقالة