The use of condensed tannins as a nutritional and medical alternative in ruminants

Abstract

Tannins are polyphenolic compounds found in many angiosperms, especially in legumes from the temperate and tropical regions. They are used by plants as a defense mechanism against being grazed by herbivores, against pathogens, and for nitrogen conservation. One of its main features is the capacity to form complex and reversible compounds with protein. There are two main groups of tannins: hydrolysable and condensed. Condensed tannins may have, either, toxic and antinutritional or beneficial effects depending on plant concentration. Reports showed that moderate amounts of condensed tannins have beneficial impacts on protein metabolism in ruminant’s nutrition, as they reduce protein ruminal degradation and increase amino acids absorption in the small intestine. Based on this information it has been suggested the use of tannins in ruminant’s diets, despite the contradictory results presented by various researchers about pros and cons when used in animal nutrition. Tannins increase body gain weight and wool production, improves reproductive efficiency in ewes, and reduces the impact of gastrointestinal parasitism and the incidence of bloat. On the other hand, some of the negative effects reported include reduction of the voluntary feed intake explained as a reduced palatability due to the astringency in saliva, affecting digestion and consequently, growth. The effects of condensed tannins over the digestive process are related with its capacity to bind with different molecules depending on its chemical structure and of the structure of molecules like cellulose, digestive enzymes, proteins, sugars and the membrane of bacteria and fungi.