Effects of Yucca schidigera and Quillaja saponaria extracts on in vitro ruminal fermentation and methane emission

An in vitro continuous incubation system was used to evaluate effects of increasing concentrations of Yucca schidigera extract (YSE) and Quillaja suponaria extract (QSE), at 0, 2, 4, and 6 ml/l, on rumen fermentation and methane production. The culture media consisted of 400 ml of strained rumen fluid collected from two ruminally cannulated non-lactating Holstein cows fed oat and alfalfa hay (1: 1, w/w) at a maintenance energy level (i.e., 55 g of DM/kg of BW0.75 daily), and 400 ml of McDougall's buffer. Treatments were in two 4 x 4 Latin square experiments for YSE and QSE. The culture media were anaerobically incubated with 10 g of a mixture of ground concentrate and oat hay (1: 1, w/w) at 39 degrees C for 24 h. Gas emission from each fermentation vessel was measured continuously by infrared methane and carbon dioxide gas analyzers. Rate and extent of methane production were reduced (P < 0.001) by YSE addition in a dose-dependent manner by up to 42% and up to 32%, respectively, whereas QSE did not effect methane production. Medium pH was not altered by YSE, but increased (P < 0.01) with QSE addition. Ammonia N concentrations were markedly reduced (P < 0.001) by YSE in a dose-dependent manner by up to 48%, whereas QSE supplementation only tended (P=0.06) to decrease NH3-N concentrations. Protozoal numbers decreased (P < 0.001) by up to 56% with YSE and by up to 41% with QSE addition. Addition of YSE and QSE increased (P < 0.001) medium optical density at 660 nm (OD660), indicating that microbial populations increased. Propionate concentration increased (P < 0.001) by up to 54% and acetate to propionate ratios decreased (P < 0.001) by YSE addition in dose-dependent manners. QSE addition increased (P < 0.05) propionate concentrations by up to 19%, but there were no differences among levels of QSE addition. Results suggest that Y. schidigera extract has a particular suppressing effect on rumen methanogenesis and that both plant extracts, Y. schidigera and Q. saponaria, may have potential as antiprotozoal agents. (c) 2006 Elsevier B.V. All rights reserved.