In vitro digestibility and fermentation kinetics of some browse plants using sheep or goat ruminal fluid as the source of inoculum

To explore the hypothesis that different ruminant species may differ in their ability to digest browse forages in the rumen, two in vitro experiments were conducted using batch cultures inoculated with rumen fluid (RF) obtained from either sheep or goats fed on the same diet (alfalfa hay). In vitro dry matter digestibility (IVD) and gas production kinetics were determined for 24 samples of leaves, flowers and fruits of five browse plant species: Erica australis; Cistus laurifolius; Quercus pyrenaica; Cytisus scoparius and Rosa canina, collected at upland sited in the province of Leَn (NW Spain) from spring to autumn. There were no IVD differences between sheep and goat RF for any of the browse plant samples. The extent of degradation in the rumen was higher (P<0.05) with goat RF for leaves and flowers of R. canina and young leaves and fruits of Q. pyrenaica, with higher values (P<0.05) with sheep RF for leaves of C. laurifolius harvested in September. Likewise, dry matter disappearance at 144 h was generally higher with goat RF and differences (P<0.05) were mainly detected for leaves and flowers of R. canina. However, although statistical differences between both sources of inoculum were not consistent among and within plant species, asymptotic gas production and gas production at 24 h were generally higher with sheep RF. Gas production rate was faster (P<0.05) with sheep RF only for young leaves of E. australis and C. scoparius and leaves of C. laurifolius collected in June and September; however, with goat RF higher (P<0.05) values were detected for flowers of C. laurifolius, fruits and mature leaves of Q. pyrenaica and flowers and young leaves of R. canina. Although some interspecies differences in the in vitro ruminal fermentative activity were detected in the present study, it can be concluded that when animals are fed the same diet, differences between sheep and goat rumen fluid used as source of inoculum can be considered of little nutritional significance.