Effects of forage legumes containing condensed tannins on methane and ammonia production in continuous cultures of mixed ruminal microorganisms

Abstract

It has been reported that some condensed tannin (CT) containing forage legumes may reduce ruminal CH4 emissions as a result of direct and/or indirect inhibition of methanogens. Dual flow continuous fermentors (working volume of 700ml) were used to determine effects of CT containing legume hays in dairy total mixed rations (TMR) on ruminal fermentation, with an emphasis on CH4 and ammonia N production. Fermentors were inoculated with filtered rumen contents and allowed to adapt to experimental diets for 6d, followed by 3d of sampling and data collection. All dietary treatments were formulated for lactating dairy cows in early lactation. Five TMR were evaluated being: (1) alfalfa (AFT), (2) cicer milkvetch (CMVT), (3) Norcen birdsfoot trefoil (NBFTT), (4) Oberhaunstadter birdsfoot trefoil (OBFTT) and (5) sainfoin (SFT). The experiment was a 5×5 Latin square design. Compared to AFT, culture pH was not influenced by most forages, but was increased (P<0.01) by feeding SFT. Compared to AFT, the molar proportion of propionate increased (P=0.03) with CMVT, but decreased (P=0.05) with SFT. Feeding CMVT decreased (P<0.01) the molar proportion of butyrate relative to AFT. Acetate to propionate ratio decreased with CMVT (P<0.01) and OBFTT (1.65; P=0.01), but increased with SFT (P<0.01) compared to AFT. Apparent digestibility of dry matter or neutral detergent fiber (aNDF) was not influenced by forage source. Compared to AFT, CH4 production decreased with other treatments (P<0.01), whereas CH4 production (expressed as mM/g aNDF digested) was only reduced (P<0.05) by CMVT and OBFTT. NH3–N concentration was lower (P<0.01) with CMVT and SFT, but not affected by NBFTT or OBFTT compared to AFT. Legume forages eliciting reductions in CH4 and NH3–N production may offer advantages in lactating dairy diets to improve nutrient utilization and environmental sustainability of dairy cattle production.This paper is part of the special issue entitled: Greenhouse Gases in Animal Agriculture – Finding a Balance between Food and Emissions, Guest Edited by T.A. McAllister, Section Guest Editors: K.A. Beauchemin, X. Hao, S. McGinn and Editor for Animal Feed Science and Technology, P.H. Robinson.