Condensed Tannin and Saponin Content of Vigna unguiculata (L.) Walp, Desmodium uncinatum, Stylosanthes guianensis and Stylosanthes scabra Grown in Zimbabwe J.J. Baloyi 1 *, N.T. Ngongoni 2 , J.H. Topps 3 , T. Acamovic 4 and H. Hamudikuwanda 2 1 Zimbabwe Open University, Masvingo; 2 Department of Animal Science, University of Zimbabwe, Harare, Zimbabwe; 3 Department of Agriculture, University of Aberdeen, Aberdeen; 4 Department of Biochemistry and Nutrition, Scottish Agricultural College, Auchincruive, UK *Correspondence: Zimbabwe Open University, 68 Hellet Street, PO Box 1210, Masvingo, Zimbabwe Baloyi, J.J., Ngongoni, N.T., Topps, J.H., Acamovic,T. and Hamudikuwanda, H., 2001. Condensed tannin and saponin content of Vigna unguiculata (L.) Walp, Desmodium uncinatum, Stylosanthes guianensis and Stylosanthes scabra grown in Zimbabwe. Tropical Animal Health and Production, 33(1), 57^66 ABSTRACT Samples of the tropical forage legumes Vigna unguiculata (L.) Walp (cowpea), Desmodium uncinatum (silverleaf desmodium), Stylosanthes guianensis (oxley ¢ne stem stylo) and Stylosanthes scabra (¢tzroy) and of natural pasture (veld) hay were analysed and ranked according to their proanthocyanidin (PA) and saponin content. Silverleaf desmodium and ¢tzroy leaf and stem samples of di¡erent ages were also separately analysed for the PA contents. All the samples analysed contained some PA but no saponins. High levels of PA were detected in silverleaf desmodium and very low levels in veld hay and cowpea. In all samples, more of the tannins were bound to protein or neutral detergent ¢bre (NDF) than were extractable, most being bound to proteins. The proportion of the unextractable PA was greater in younger than in mature materials. Keywords: cowpea, desmodium, ¢tzroy, forage, legume, proanthocyanidin, saponin, stylo, tannin Abbreviations: ADF, acid detergent ¢bre; ADL, acid detergent lignin; CP, crude protein; MT, Mimosa tannin; NDF, neutral detergent ¢bre; PA, proanthocyanidin(s) INTRODUCTION Forage legumes are generally good sources of energy and protein for grazing ruminants, but sometimes the presence of an array of secondary compounds or antinutritional factors in these feeds, such as glucosinolates, tannins, saponins, non- protein amino acids, lectins, alkaloids or gossypol, result in ruminant production being less than expected. Some of these factors may cause acute adverse e¡ects in ruminants. High contents of condensed tannins in forage legumes have been suggested to be possible causes of reduced nutritive value for ruminants (Ahn et al ., 1989; Palmer and Schlink, 1992). The e¡ects of polyphenolics on the nutritive value of legumes in ruminants may vary from merely a¡ecting the species composition of the micro£ora Tropical Animal Health and Production, 33 (2001) 57^66 # 2001 Kluwer Academic Publishers. Printed in the Netherlands 57