In situ and in vitro methods have been developed with the primary aim to estimate digest­ibility of feeds for diet formulation in ruminant livestock production systems. The objective with this study was to compare digestion rate (kd) of NDF for different feeds estimated with the in situ method or derived from an automated gas in vitro system. Further, in vitro true digestibility of the feed samples incubated in Alter bags or freely floated was compared, and kd for insoluble and soluble components of those feeds were estimated. In addition, proportion of methane to total gas of the samples was measured in the automated gas in vitro system.