Effects of Leucaena condensed tannins of differing molecular weights on in vitro CH4 production

Condensed tannins (CT) exhibit nutritional, environmental and veterinary benefits in ruminant production. It is known that effects of CT on animal nutrition is multi-factorial, but their molecular weight (MW) and/or chemical structures play a key role in their biological activity. The average MW of five CT fractions obtained from Leucaena hybrid-Bahru (LLB) was determined using mass quadrupole time-of-flight liquid chromatography/mass spectrometry. CT within each fraction had varying degrees of polymerization with up to hexamers and molecular weights of 1348.80 Da identified in the first fraction, and 494.56 Da in the fifth fraction. Results show that CT fractions with the highest MW had in the highest inhibition of CH4 production, being 62% lower than the control. In addition, the amount of CH4 as a proportion of total gas also decreased with CT compared to control, suggesting a direct effect of CT on CH4 production with those of higher MW exhibiting anti-methanogenic activity. This article is part of the special issue entitled: Greenhouse Gases in Animal Agriculture Finding a Balance between Food and Emissions, Guest Edited by TA. McAllister, Section Guest Editors; K.A. Beauchemin, X. Hao, S. McGinn and Editor for Animal Feed Science and Technology, P.H. Robinson. (C) 2011 Elsevier B.V. All rights reserved.