Abstract:The in vitro gas production technique was used to predict rumen fermentable organic matter, gas production kinetics, organic matter digestibility as well as metabolizable energy were evaluated in green shoot, leaves, fruits flesh and seed cakes of Ziziphus spina-christi tree. A gas production was measured by incubating samples in buffered rumen fluid from cannulated steer for 72 h. Total gas production was recorded at 0,3,6,9,12,24, 48, and 72 h of incubation periods and kinetics of gas production was described. 01),while fruits flesh contained the highest ether extract(72.39±0.03).The maximum gas volume was highest for fruits flesh followed by seed cakes, green shoot and leaves after 24hr of incubation. In this study flesh had a significantly higher (P<0.05) gas production from rapid soluble fraction (a) than the other parts, while Ziziphus spina-christi leaves showed the highest gas production from slowly degradable fraction (b).Organic matter digestibility range was (51.90-43.79%) and Metabolisable energy was found to be