Responses to condensed tannins of flowering sulla (Hedysarum coronarium L.) grazed by dairy sheep Part 2: Effects on milk fatty acid profile A. Cabiddu ⁎, G. Molle, M. Decandia, S. Spada, M. Fiori, G. Piredda, M. Addis AGRIS Sardegna, Dipartimento per la Ricerca nelle Produzioni Animali, 07040 Olmedo, Italy article info abstract Article history: Received 9 April 2008 Received in revised form7 November 2008 Accepted 17 November 2008 A grazing experiment was undertaken to evaluate the effect of PEG supplementation on the fatty acid composition of milk from Sarda sheep grazing sulla. Twenty-four late-lactating sheep (12 per group), were paired and split into two groups: group control (CON), dosed daily with a quenching gun with 200 ml of water, and group PEG, dosed with 200 ml of a 50/50 w/v water solution of PEG. The sheep grazed two 0.8 ha plots of sulla under a rotational grazing scheme. The contents of c-9, t-11 CLA and t-11 C18:1 in milk fat were on average 40% higher (P b 0.01) in the PEG group than in the CON group. This can be explained by the higher biohydrogenation activity of ruminal bacteria in the PEG group, due to the partial inactivation of the tannins. Odd- branched chain fatty acids (OBCFA) were higher in PEG than in the control group (+20%; P b 0.01) and this confirms the hypothesis that tannin in sulla reduced ruminal microbial activity. Both linoleic (C18:2 c-9 c-12) and linolenic (C18:3 c-9 c-12 c-15) fatty acids were lower (P b 0.05) in milk from PEG, than in the CON-group (-12% and -30% for linoleic and linolenic acids, respectively). The mitigating effect on tannins of PEG increased the ratio of ω6/ω3 by 24%; (P b 0.01) and total trans FA content in milk by 20% (P b 0.01). In conclusion, condensed tannins in sulla at flowering are conducive to lower c-9, t-11 CLA and t-11 C18:1 but also lower total trans FA, ω6/ω3 ratio and higher linoleic and linolenic acid. © 2008 Elsevier B.V. All rights reserved. Keywords: Hedysarum coronarium PEG Milk Sheep OBCFA CLA Tannins 1. Introduction There is renewed interest in forage legumes, because of their important role in sustainable feeding systems. They are able to fix nitrogen and have potentially a high feeding value for ruminants (Rochon et al., 2004). Sulla (Hedysarum coronarium L.) is a legume with a high nutritive value (Terrill et al., 1992; Molle et al., 2003). It usually contains a moderate level of condensed tannins (CT, 20–40 g kg DM -1 ). These compounds have beneficial effects on the net uptake of amino-acids and parasite burden resilience in certain circumstances, depending, among other factors, on their concentration and source (Mueller-Harvey, 2006). By contrast, in other circumstances they have negative effects on ruminant nutrition because they reduce voluntary feed intake (VFI), proteins, structural carbohydrates digest- ibility and intestinal enzymes activity, or they cause illness (e.g. Silanikove et al., 1994). Reduction of diet digestion is attributed to the formation of stable complexes between CT and protein or/and carbohydrates, even though the great diversity of tannin in nature means that it is difficult to generalise about their effects. Indeed, some tannins cause lesions in the gut mucosa (Robbins et al., 1991), but can be degraded. Others cause rapid reduction of VFI through the emetic mechanism of the nervous system (Provenza et al., 1990). Tannins may decrease DM digestibility through their bacteriostatic and bactericidal effects on rumen microbes (Henis et al., 1964). Inhibition increases with the increase in the degree of tannin polymerization. The effects of CT on the growth of rumen bacteria and on microbial proteolysis have been recently described by Min et al. (2005), who clearly showed the reduction of the rate of proteolysis and the Livestock Science 123 (2009) 230–240 ⁎ Corresponding author. Tel.: +39 079 387236; fax: +39 079 389450. E-mail address: acabiddu@agrisricerca.it (A. Cabiddu). 1871-1413/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.livsci.2008.11.019 Contents lists available at ScienceDirect Livestock Science journal homepage: www.elsevier.com/locate/livsci