Tannins In Feedstuffs For Simple- Stomached Animals
A. J. M. JANSMAN
Agricultural University, Department of Animal Nutrition, Haagsteeg 4, 6708 PM Wageningen, The Netherlands
TNO-Nutrition and Food Research, Department of Animal Nutrition and Physiology (ILOB), P.O. Box 15, 6700 AA Wageningen, The Netherlands
The term ‘tannin’ was originally used to describe substances in vegetable extracts used for converting animal skins into stable leather (Seguin, 1796). The substances essential in the tanning process (tannins) were later identified as polyphenolic compounds with various molecular weights and of varying complexity. It was also found that these polyphenolic compounds bind strongly not only to hide protein, but also to other proteins and to macromolecules such as polysaccharides. Tannins are present in a large number of products of vegetable origin used as human foods or animal feeds. During the past century a number of adverse nutritional effects has been attributed to tannins. This review will first summarize current knowledge of the chemistry, occurrence and natural function of plant tannins. Subsequently, special attention will be given to the harmful effects of tannins in animal feeds, particularly in simple-stomached farm animals such as poultry and pigs. The nutritional effects of tannins in ruminants have been reviewed recently by Kumar & Singh (1984), Mangan (1988), Kumar & Vaithiyanathan (1990), Leinmuller el al. (1991) and Menke & Leinmiiller (1991).