View article

The effects of steroidal saponins (SAP) isolated from Yucca schidigera extract on ruminal bacteria and fungi were investigated in pure culture studies. Prevotella bryantii, Ruminobacter amylophilus, Selenomonas ruminantium and Streptococcus bovis were cultured through ten 24‐h transfers in ruminal fluid medium containing 0 or 25 µg SAP ml⁻¹ (measured as smilagenin equivalents). The four strains, each non‐exposed or pre‐exposed to SAP, were then inoculated into medium containing 0 or 250 µg smilagenin equivalents ml⁻¹ and 24‐h growth curves were determined. The cellulolytic ruminal bacteria Ruminococcus flavefaciens, Fibrobacter succinogenes and Rc. albus were cultured for 72 h on Whatman no. 1 filter paper in medium containing 0, 9, 90 or 180 µg SAP ml⁻¹ for the determination of filter paper digestion and endoglucanase activity. The ruminal bacteria differed in their responses to SAP …