In vitro dry matter digestibility (IVDMD) and gas production kinetics of the foliage of Erica australis, Cistus laurifolius, Quercus pyrenaica and Rosa canina were studied. Pre-incubation in artificial, sheep or goat saliva was followed by incubation in buffered sheep rumen liquid. The extent of degradation in the rumen and rate of gas production were determined from gas production parameters. Pre-incubation affected IVDMD only in Q. pyrenaica and R. canina, with the higher values for sheep saliva. The rate of gas production was lower for E. australis and Q. pyrenaica with goat saliva. Gas production after 24 h was higher with sheep saliva for most of the species. The extent of degradation in the rumen was similar with both saliva for C. laurifolius and Q. pyrenaica; in R. canina it was higher in goats. In vitro ruminal fermentative activity seemed to be affected by the pre-incubation in different saliva sources.