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Conference paper - Peer-reviewed, 2009

Effect of wilting, silage additive, PEG treatment and tannin content on the distribution of N-fractions after ensiling of three varieties of Sainfoin (Onobrychis viciifolia)

Lorenz, Martin; Eriksson, Torsten; Udén, Peter


Introduction Sainfoin is a tanniniferous, leguminous plant that has potentially beneficial effects on protein utilization in ruminants (McAllister, Martinez et al. 2005). Since ensiling causes major protein breakdown, our objectives were to study the effects of wilting, treatment with Promyr (PM; a commercial mixture of propionic and acetic acid) and plant tannin levels on the buffer soluble nitrogen (BSN) with or without polyethylene glycol (PEG). Material and Methods The Sainfoin varieties were Cotswold Common, Reznos and Teruel. A grass/clover mixture (1:1) served as a tannin-free control. The plant material (80 g) was ensiled in duplicate mini-silos for 60 days at 20°C, either fresh or after drying to 50% dry matter (DM) at 40°C. PEG and PM were applied before ensiling and PEG was used as an indirect measure of tannin effect during ensiling. The silages were analyzed for total N, BSN, trichloroacetic acid non-precipitable N (TCA-NPN), α-amino acid-N (AA-N), NH3, DM, extractable tannins (ET) and protein bound tannins (PBT). Tannins were measured by a modified method of Terrill et al. (1992). Results and Discussion Total N ranged from 22 to 26 g/kg DM depending on variety and treatment. Cotswold Common had the highest total N, and Reznos had the overall lowest ratio of BSN:total N. PEG increased and PM decreased the level of BSN in the silages (p<0.001). The PM treatment produced lower BSN, TCA-NPN and NH3 (p<0.05) as compared with no additive. Addition of PEG increased the BSN-proportion 1.8- and 2.6-fold for wilted and un-wilted silages, respectively. This suggests a strong tannin-protein binding effect in Sainfoin. Correlations between tannin levels (ET and PBT) and BSN were poor in the non-PEG silages. Conclusion Promyr lowered silage BSN contents and PEG treated Sainfoin silages showed higher BSN contents. However, the correlation between tannin content and silage N-fractions were poor in the non-PEG treatments, indicating qualitative attributes of tannins, rather than quantitative. References McAllister, T. A., T. Martinez, et al. 2005. Characterization of condensed tannins purified from legume forages: Chromophore production, protein precipitation, and inhibitory effects on cellulose digestion. Journal of Chemical Ecology 31(9):2049-2068. Terrill, T. H., A. M. Rowan, et al. 1992. Determination of extractable and bound condensed tannin concentrations in forage plants, protein concentrate meals and cereal grains. Journal of the Science of Food and Agriculture 58(3): 321-329

Published in


XVth Int. Silage Conf