In vitro study of the effects of condensed tannins in sainfoin on the digestive process in the rumen at two vegetation cycles.

Abstract of accepted paper in the Animal Feed Science and Technology, ANIFEE-10-3225R3 2011.

In vitro study of the effects of condensed tannins in sainfoin on the digestive process in the
rumen at two vegetation cycles.

K. Theodoridou, J. Aufrere, V. Niderkorn, D. Andueza, A. Le Morvan, F. Picard and R. Baumont. INRA Unite´ de Recherches sur les Herbivores, Centre de Clermont-Ferrand – Theix, 63122, Saint-Gene`s-Champanelle, France.

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 condensed 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 fermentation times increased gas production of leaves, stems and whole plant (P<0.001). At 3.5 h, PEG addition resulted in higher CH4 values for stems and leaves at two vegetation cycles (P<0.01). The CO2:CH4 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 CH4 production, or the CO2:CH4 ratio, at either 3.5 or 24 h of incubation. At both incubation periods, in vitro true organic matter 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) NH3-N for leaves and stems in both vegetation cycles. For the whole plant, PEG resulted in higher NH3-N content (P<0.001) at both 3.5 and 24 h of incubation. Utilisation of sainfoin curbs CH4 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 .