Small Ruminant Research 121 (2014) 168–174 Contents lists available at ScienceDirect Small Ruminant Research jou rn al h om epa ge : w ww.elsevier.com/locate/smallrumres Effect of nitrate and fumarate in Prosopis cineraria and Ailanthus excelsa leaves-based diets on methane production and rumen fermentation K. Pal a , A.K. Patra a,∗ , A. Sahoo b , G.P. Mandal a a Department of Animal Nutrition, Faculty of Veterinary and Animal Sciences, West Bengal University of Animal and Fishery Sciences, 37 K. B. Sarani, Belgachia, Kolkata 700037, India b Central Sheep and Wool Research Institute, Division of Animal Nutrition, Avikanagar 304501, Rajasthan, India a r t i c l e i n f o Article history: Received 27 December 2013 Received in revised form 13 August 2014 Accepted 14 August 2014 Available online 24 August 2014 Keywords: Nitrate Fumarate Tree leaves Methane Rumen fermentation In vitro gas production Sheep a b s t r a c t This study investigated the effect of nitrate and fumarate in Prosopis cineraria (khejri) and Ailanthus excelsa (ardu) leaves-based diets on methane production, feed degradability and rumen fermentation in vitro. The treatments were arranged in a 4 × 3 × 2 factorial design. The factors studied were four diets: cenchrus grass (Cenchrus ciliaris) hay (CC), cenchrus hay, ardu and khejri leaves (50:25:25; CAKC), cenchrus hay and ardu leaves (50:50; CAC), and cenchrus hay and khejri leaves (50:50; CKC) as roughage sources, each supplemented with a concentrate mixture; three additives: control (without any additives), nitrate (5 mM) and fumarate (10 mM); and two ratios of roughage to concentrate (R:C): 70:30 and 40:60. Methane production was lowered (P < 0.05) by the grass hay and leaves-based diets (CAKC, CAC and CKC) than CC (56, 48, 39 and 32 ml/g digested organic matter (DOM) for CC, CAKC, CAC and CKC, respectively for low R:C diet; 66, 64, 58 and 52 ml/g DOM for CC, CAKC, CAC and CKC, respectively for high R:C diet), but the extent of inhibition varied depending upon diet type. Addition of nitrate and fumarate suppressed methane production additively in leaves-based diets, and this response was markedly higher for low R:C diet than high R:C diet. In general, leaves-based diets had greater degradability than the CC, and the effect was more pronounced for high R:C (i.e. high leaves) diets compared with low R:C diets (65% and 59% for leaves-based diets and CC, respectively for high R:C diet; 74% and 68% for leaves-based diets and CC, respectively for low R:C diet). Nitrate decreased the degradability of organic matter (OM) compared with control for both low (5.6%) and high (6.1%) R:C diets. Fumarate lowered OM degradability by 5.7% for high R:C diets. Nitrate increased ammonia concentration compared with CC and fumarate. Ammonia concentration was higher for leaves-based diets than CC except for CKC plus nitrate. Nitrate (12.8% and 8.4% for high and low R:C diets, respectively) and fumarate (11.6% and 18.8% for high and low R:C diets, respectively) increased total volatile fatty acid concentrations and microbial biomass yields, which were greater for leaves-based diets than the CC. This study demonstrated that addition of fumarate and nitrate in diets containing P. cineraria and A. excelsa leaves may additively decrease methane production and improve rumen fermentation. © 2014 Elsevier B.V. All rights reserved. ∗ Corresponding author. Tel.: +91 33 25569234; fax: +91 33 25571986. E-mail address: patra amlan@yahoo.com (A.K. Patra). 1. Introduction Livestock production systems contribute greenhouse gas emissions (GHG) considerably to the atmosphere, http://dx.doi.org/10.1016/j.smallrumres.2014.08.004 0921-4488/© 2014 Elsevier B.V. All rights reserved.