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¯uid medium containing 0 or 25 mg SAP ml À1 (measured as smilagenin equivalents). The four strains, each non-exposed or pre-exposed to SAP, were then inoculated into medium containing 0 or 250 mg smilagenin equivalents ml À1 and 24-h growth curves were determined. The cellulolytic ruminal bacteria Ruminococcus¯avefaciens, Fibrobacter succinogenes and Rc. albus were cultured for 72 h on Whatman no. 1 ®lter paper in medium containing 0, 9, 90 or 180 mg SAP ml À1 for the determination of ®lter paper digestion and endoglucanase activity. The ruminal bacteria differed in their responses to SAP. Steroidal saponins in the medium reduced the growth of Strep. bovis (P < 0Á01 at 2, 3, 4, 5, 6 and 8 h), P. bryantii (P < 0Á05 at 4, 5, 6, 8, 10 and 24 h) and Rb. amylophilus (P < 0Á05 at 14 and 24 h), but the growth of S. ruminantium was enhanced (P < 0Á05) at 10, 14 and 24 h. The growth curves of all four non-cellulolytic species were similar (P > 0Á05) between pre-exposed and non-exposed cultures and the concentrations of total SAP and soluble (deglycosylated) SAP in the liquid fraction were unchanged (P > 0Á05) over time. Steroidal saponins inhibited the digestion of ®lter paper by all three cellulolytic bacteria, but F. succinogenes was less (P < 0Á05) sensitive to SAP and more (P < 0Á05) effective at deglycosylating SAP than were Rc.¯avefaciens or Rc. albus. Transmission electron microscopy revealed that SAP altered the cell walls of the SAP-inhibited non-cellulolytic bacteria. The ruminal fungi, Neocallimastix frontalis and Piromyces rhizin¯ata, were cultured on ®lter paper in medium containing 0, 0Á45, 2Á25 or 4Á5 mg SAP ml À1 . Filter paper digestion by both fungi was completely inhibited by 2Á25 mg SAP ml À1

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Two continuous culture (CC) systems, the rumen simulation technique (Rusitec) and a dual-flow (DF) fermenter, were used to evaluate effects of the essential oil from cinnamon leaf (CIN) on rumen microbial fermentation. Incubations (d 1 through 8 for adaptation and d 9 through 16 for sampling) were conducted concurrently in the 2 systems, with CIN added at 0 (control) and 500 mg/L of rumen fluid culture. Eight Rusitec (920 mL; dilution rate = 2.9%/h) and 6 DF (1,300 mL; dilution rate = 6.3%/h) fermenters were randomly assigned to treatment. Inoculum was prepared from 4 ruminally cannulated lactating Holstein cows fed a total mixed ration consisting of 51% forage and 49% concentrate (dry matter basis). Ruminal pH, total volatile fatty acid (VFA) concentration, and diet digestibility were reduced by CIN addition in the Rusitec but were not affected by CIN administration in the DF. The addition of CIN in the Rusitec decreased apparent N disappearance, NH3-N concentration, and molar proportions of branched-chain VFA. In contrast, in the DF no effect of CIN was observed on apparent N degradation, NH3-N concentration, and molar proportion of branched-chain VFA. In the Rusitec, the molar proportion of acetate was similar between treatments on d 9 and 13, but was lower from d 10 to 12 and higher on d 14 to 16 with CIN than with control (interaction of treatment x sampling day). The molar proportion of acetate remained unaffected by CIN addition in the DF. In both CC systems, the molar proportion of propionate was decreased whereas that of butyrate was increased by CIN addition. In the DF, CIN decreased microbial N flow and efficiency of microbial protein synthesis. Protozoa numbers were lower with CIN than with control in both CC fermenters. In the Rusitec, CIN increased 15N enrichment in total bacterial fractions, but no effect was observed on the production of microbial N. This study showed that CIN exhibited antimicrobial activity in both CC systems, but the effects were more pronounced in the Rusitec than in the DF system. These differences are likely a reflection of the higher dilution rate in the DF resulting in a lower effective concentration of CIN than in Rusitec. Based on these changes in rumen microbial fermentation, supplementation of CIN at the concentration evaluated in this study may not be nutritionally beneficial to ruminants.

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Foam stability related to pasture bloat from alfalfa pastures might be reduced by introducing a gene that stimulates the accumulation of mono-⁄ polymericanthocyanidin. The objective of this study was to determine the foam formation (at 0 min) and stability (at 150 min) from aqueous leaf extracts of three transgenic Lc-alfalfa progeny (BeavLc1, RambLc3 and RangLc4), parental non-transgenic (NT) alfalfa and AC Grazeland (bloat-reduced cultivar) harvested at 07:00 or 18:00 h. Initial and final foam volumes at 07:00 h were lower for AC Grazeland compared with all other treatments and lower for RangLc4 compared with the other two Lc-progeny at 0 min and NT-alfalfa at 150 min. At 18:00 h, initial foam volume was larger for NT-alfalfa and final foam volume was larger for RambLc3 compared with AC Grazeland, BeavLc1 and RangLc4. Spectroscopic vibration associated with carbohydrates increased initial foam volume and stability. More amide I relative to amide II, fewer a-helices relative to b-sheets and leaf extract ethanol-film and protein content increased initial foam volume but did not stabilize it. Spectroscopic vibration associated with all carbohydrates other than structural carbohydrates was more important than vibration from protein structures for foam formation and stabilization. In conclusion, Lc-alfalfa accumulated anthocyanidin and had reduced foaming properties compared with parental NT alfalfa but AC Grazeland and RangLc4 had the lowest foaming properties.