Garlic oil and its principal component diallyl disulfide fail to mitigate methane, but improve digestibility in sheep

One focus of current ruminant research is identification of feed supplementation strategies for mitigating enteric CH4 production that do not impair rumen fermentation. Previous in vitro studies have indicated a potential anti-methanogenic activity of garlic (Allium sativum), garlic oil (GO), and its main compound diallyl disulfide (DADS). In our study, effects of supplementation of a standard hay and concentrate diet with 5 g GO or 2 g DADS/kg dietary dry matter (DM) were tested in sheep in a duplicated 3 x 3 Latin square design experiment with three 23 d periods. Respiratory measurements were on d 17 and 18. Dietary supplementation with GO or DADS had no influence on the amount of CH4 produced (27 g/d). When rates of CH4 production/kg OM digested were compared, DADS, but not GO, tended (P=0.09) to decrease CH4 production compared to control. DM intake was not affected by GO or DADS, although concentrate intake was slightly decreased (P=0.10) with GO compared to control. DADS increased (P=0.02) digestibility of OM and aNDFom (P=0.03), as well as energy utilization (P=0.03) compared to control. Low palatability and lack of effect on either CH4 mitigation or energy use efficiency indicate that a GO supplemented concentrate is of little relevance in practice. As DADS supplementation only tended to decrease CH4 formation relative to OM digested, it too is limited use as a means of CH4 mitigation. However, DADS supplementation improved digestibility and energy use efficiency. 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.