Methane mitigation from ruminants using tannins and saponins

Abstract

MethanereductionontrulydegradedsubstratebasisOMD Organic matter digestibilityPSM Plant secondary metabolitesQSE Quillaja saponaria extractSCFAs Short-chain fatty acidsTP Total phenolsTT Total tanninsIntroductionThe ruminal methane production is a by-product of themicrobial digestive process and represents a loss of 2–12%of the feed energy. Furthermore, emission of methane isconsidered as one of the most important global environ-mental issues (IPCC 2001). Therefore, decreasing methaneproduction is desirable for reducing the greenhouse gasemission with improved efficiency of the digested energyutilization (Johnson and Johnson 1995). A previous reportby Kurihara et al. (1999) indicated that methane energy lossin cattle fed on tropical forage diets was higher than inthose fed on temperate forage diets, due to relative highlevels of fibre and lignin and a low level of non-fibrecarbohydrate in tropical forages. Also, the livestock indeveloping countries are predominantly maintained on ahigh-roughage diet with little or no concentrate resulting inincreased ruminal methanogenesis. Therefore, the use ofbrowse species containing secondary compounds as feedsupplement rich in plant secondary metabolites (PSM) forruminants in many parts of the tropics is increasing in orderto improve animal performance and reduce methane(Abdulrazak et al. 2000). Tannins and saponins constitutethe major classes of PSM that are currently under researchin a number of laboratories. The antimicrobial action andeffects on rumen fermentation of these compounds dependon their nature, activity and concentration in a plant or plant