Animal Feed Science and Technology 170 (2011) 147–159 Contents lists available at SciVerse ScienceDirect Animal Feed Science and Technology journal homepage: www.elsevier.com/locate/anifeedsci In vitro study of the effects of condensed tannins in sainfoin on the digestive process in the rumen at two vegetation cycles Katerina Theodoridou, Jocelyne Aufrère ∗ , Vincent Niderkorn, Donato Andueza, Aline Le Morvan, Fabienne Picard, René Baumont INRA UR1213 Herbivores, Centre de Clermont-Ferrand – Theix, 63122 Saint-Genès-Champanelle, France a r t i c l e i n f o Article history: Received 29 November 2010 Received in revised form 25 August 2011 Accepted 4 September 2011 Keywords: Sainfoin In vitro gas production Tannins Polyethylene glycol Methane Ruminal fermentation a b s t r a c t One approach to reducing enteric production of greenhouse gases (GHG; i.e., nitrous oxide and methane) is to feed tanniniferous forage plants such as sainfoin. The objective of this study was to investigate, in vitro, effects of the content and structural characteristics of con- densed tannins (CT) in the whole plant, leaves and stems of sainfoin (Onobrychis viciifolia) on the digestive process in the rumen. Sainfoin, studied during the first vegetation cycle at the end of flowering, and during the second vegetation cycle at the start of flowering, was incubated in serum bottles containing buffered rumen fluid for 3.5 and 24 h. To assess effects of CT, incubations were with and without added polyethylene glycol (PEG), to neutralise CT effects. Biological activity and prodelphinidin (PD) content were higher (P<0.001) in leaves than in stems, but cis value was lower (P<0.01). At 3.5 h of incubation, gas production was higher for stems than leaves (P<0.05), but at 24 h only tended to be higher for leaves than stems (P=0.096), at the end of flowering. The presence of PEG at both short and long fer- mentation times increased gas production of leaves, stems and whole plant (P<0.001). At 3.5 h, PEG addition resulted in higher CH 4 values for stems and leaves at two vegetation cycles (P<0.01). The CO 2 :CH 4 ratio was lower (P<0.01) at 3.5 h and higher at 24 h (P<0.01) with added PEG. No effect of PEG on whole plant CH 4 production, or the CO 2 :CH 4 ratio, at either 3.5 or 24 h of incubation. At both incubation periods, in vitro true organic mat- ter digestibility (IVTOMD) was higher for leaves than stems (P<0.001), and decreased with added PEG at 24 h (P<0.001). For the whole plant, PEG had no effect on IVTOMD at either 3.5 or 24 h of incubation. At 3.5 h, PEG resulted in higher N disappearance (ND) at both vegetation cycles (P<0.01), whereas values were higher at the second one (P<0.001). Mean volatile fatty acid production was higher for leaves than stems (P<0.01) and increased with PEG (P<0.001) for both vegetation cycles at 3.5 and 24 h of incubation. For both incubation periods, PEG increased (P<0.001) NH 3 –N for leaves and stems in both vegetation cycles. For the whole plant, PEG resulted in higher NH 3 –N content (P<0.001) at both 3.5 and 24 h of incubation. Utilisation of sainfoin curbs CH 4 production without altering its organic matter digestibility and N value, but research on the nutritional impact of CT must not only be based on CT content in plant tissue, but include structure-activity considerations of CT. © 2011 Elsevier B.V. All rights reserved. Abbreviations: ADF, acid detergent fibre expressed inclusive of residual ash; aNDF, neutral detergent fibre assayed with a heat-stable amylase and expressed inclusive of residual ash; BSA, bovine serum albumin; BW, body weight; CT, condensed tannins; Dcell, pepsin–cellulase digestibility; DM, dry matter; GP, gas production; HT, hydrolysable tannins; IVTOMD, in vitro true OM digestibility; mDP, mean degree of polymerisation; ND, N disappearance; OM, organic matter; OMD, OM digestibility; PC, procyanidins; PD, prodelphinidins; PEG, polyethylene glycol; PP, part of the plant; RDA, radial diffusion assay; T, treatment; VC, vegetation cycle; VFA, volatile fatty acids; WSC, water-soluble carbohydrates. ∗ Corresponding author. Tel.: +33 473 62 40 72; fax: +33 473624273. E-mail address: aufrere@clermont.inra.fr (J. Aufrère). 0377-8401/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.anifeedsci.2011.09.003