Tannins in Acacia cyanophylla Lindl. leaves : their effect on digestion by sheep fed alfalfa hay-based diets H. Ben Salem, A. Nefzaoui, H. Abdouli and L. Ben Salem Ann. Zootech., 44 Suppl. 1 (1995) 228 DOI: 10.1051/animres:199505196