Animal Feed Science and Technology 223 (2017) 30–41 Contents lists available at ScienceDirect Animal Feed Science and Technology journal homepage: www.elsevier.com/locate/anifeedsci Potential of mimosine of Leucaena leucocephala for modulating ruminal nutrient degradability and methanogenesis Y.A. Soltan a,∗ , A.S. Morsy b , R.C. Lucas c , A.L. Abdalla c a Alexandria University, Faculty of Agriculture, Animal Production Department, Alexandria, Egypt b City of Scientific Research and Technological Applications, Arid Lands Cultivation Research Institute, Livestock Research Department, New Borg El-Arab, Alexandria, Egypt c University of Sao Paulo, Centre for Nuclear Energy in Agriculture, Laboratory of Animal Nutrition, Piracicaba, Brazil a r t i c l e i n f o Article history: Received 15 June 2016 Received in revised form 6 November 2016 Accepted 9 November 2016 Keywords: Condensed tannins Mimosine activity Fibre degradability Methane production a b s t r a c t Two in vitro assays were accomplished to assess whether low or high mimosine natu- rally found in leucaena (Leucaena leucocephala), contribute to methane (CH 4 ) suppression. The first assay aimed to detect the effects of leucaena samples containing low or high mimosine levels on tannin bioactivity and ruminal CH 4 production. Samples contain- ing 43.9 ± 1.9 g condensed tannin (CT)/kg DM were divided into two groups based on their mimosine contents (n = 4/group): low (2.3 ± 0.1) and high (11.1 ± 1.5) g mimosine/kg DM. Leucaena incubations were made with or without polyethylene glycol (PEG). In the second assay, two leucaena samples similar in CT content and chemical compo- sition were selected from the first assay to examine the effect of level of mimosine naturally found in leucaena, as well as the direct effect of mimosine when added to Tifton (Tifton 85; Cynodon dactylon (L.) and lucerne (Medicago sativa L.) hays on rumi- nal fermentation and nutrient degradation. The results of the first assay showed that leucaena containing low mimosine with or without PEG decreased (P < 0.01) gas produc- tion (GP), but presented higher values of the percent increase in gas (P = 0.03) and CH 4 (P < 0.01) production after PEG addition compared to leucaena containing high mimo- sine. The addition of PEG in the second in vitro assay enhanced GP (P = 0.007) and CH 4 (P < 0.05) by both types of leucaena, while decreased (P = 0.01) propionate, and increased (P = 0.003) C2/C3 and NH 3 N (P = 0.02) concentrations by leucaena containing low mimo- sine compared with PEG non-supplemented leucaena. However, such an effect did not occur by leucaena containing high mimosine. L-mimosine recorded 27% (P = 0.02) and 10% (P = 0.08) CH 4 reduction when supplemented at a high level with Tifton and lucerne, respectively, while enhanced (P < 0.05) the true degradability of organic matter (TDOM), acetate and NH 3 N, compared with zero mimosine supplementation. Forages without any supplementation also affected the ruminal fermentation; similar reduction (P < 0.05) of CH 4 production was found for both leucaena samples compared to Tifton and lucerne. Abbreviations: ADFom, ash-free acid detergent fibre; AOAC, Association of Official Analytical Chemists; aNDFom, ash-free neutral detergent fibre treated with heat-stable amylase expressed exclusively of residual ash; C2/C3, acetate to propionate ratio; CH4, methane; CP, crude protein; CT, condensed tannin; DHP, dihydroxy pyridine; DM, dry matter; DADF, degraded acid detergent fibre; DNDF, degraded neutral detergent fibre; GP, gas production; lignin(sa), lignin determined by solubilisation of cellulose with sulfuric acid; OM, organic matter; PEG, polyethylene glycol; PF, partitioning factor; SCFA, short-chain fatty acids; TDOM, truly degraded organic matter. ∗ Corresponding author. E-mail address: uosra eng@yahoo.com (Y.A. Soltan). http://dx.doi.org/10.1016/j.anifeedsci.2016.11.003 0377-8401/© 2016 Elsevier B.V. All rights reserved.