Animal Feed Science and Technology 122 (2005) 173–186 Benefit from the association of small amounts of tannin-rich shrub foliage (Acacia cyanophylla Lindl.) with soya bean meal given as supplements to Barbarine sheep fed on oaten hay  H. Ben Salem a,∗ , H.P.S. Makkar b , A. Nefzaoui a , L. Hassayoun a,c , S. Abidi a a Institut National de la Recherche Agronomique de Tunisie, Laboratoire des Productions Animales et Fourrag` eres, Rue H´ edi Karray, 2049 Ariana, Tunisia b Animal Production and Health Section, Joint FAO/IAEA Division, International Atomic Energy Agency, Vienna, Austria c Ecole Sup´ erieure d’Agriculture de Mateur, 7030 Mateur, Tunisia Abstract Two trials were conducted to test the hypotheses that (i) feeding small amount of a tanniniferous shrub foliage (Acacia cyanophylla Lindl., acacia) increases the proportion of rumen undegradable protein, and consequently benefits growth performance in Barbarine lamb; and (ii) such positive effect depends on the timing of feeding tannin source (i.e. acacia) relative to protein source (soya bean meal, SBM). Total (TT) and condensed tannin (CT) concentrations in air-dried acacia leaves used in this study averaged 29 g tannic acid and 48 g leucocyanidin equivalents per kg dry matter (DM), respectively. In trial 1, rumen fistulated ewes received oaten hay (hay) ad libitum and 200g SBM (D1), D1 and 100 g acacia fed with the SBM (D2, mixed strategy) or as D2, but the SBM fed 1 h later than acacia when acacia was consumed completely (D3, sequential strategy). Hay intake, diet Abbreviations: CP, crude protein; CPD, crude protein digestibility; CT, extractable condensed tannins; DM, dry matter; N, nitrogen; NDFom, neutral detergent fibre not assayed with a heat stable amylase and expressed exclusive of residual ash; NH 3 -N, ammonia nitrogen; OM, organic matter; SBM, soya bean meal; TP, total phenols; TT, total tannins; TVFA, total volatile fatty acids  This paper is part of the special issue entitled Predicting and Improving the Safety and Efficiency of Feeding Ruminants on Tanniniferous Tree Foliage, Guest Edited by Dr. Harinder P.S. Makkar. ∗ Corresponding author. Tel.: + 216 71 230 024; fax: +216 71 231 592. E-mail address: bensalem.hichem@iresa.agrinet.tn (H. Ben Salem). 0377-8401/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.anifeedsci.2005.04.012