Tannins and their effects on animal nutrition – A review

Abstract

A general knowledge on food and on its production levels is critical for the correct management of animal feeding systems. The reduced availability and quality of food during the dry season, including the presence of anti-nutritional substances, result in low productivity of livestock. These substances reduce food consumption and digestibility, resulting in body weight and production losses. Tannins are anti-nutritional substances frequently found in plants, and forage in particular. There are many studies that determine the significance of tannins in animal nutrition and plant toxicology, as tannins may be either benefic or hatmful to animals that ingest them. So, there is a need to know the relationships of tannins with other molecules, and their effects on food ingestion and digestion. This knowledge will allow to explain their potential to positively or negatively affect animal performance. Tannins are water soluble polyphenols originated from plants, that present high molecular weight, usually between 500 and 3000 Daltons. These polyphenols show the ability to bound with, and precipitate, many types of protein, polysaccharides and amino acids. Tannins can be classified as hydrolysable and non-hydrolysable or condensed. This review has the objective to describe the types of tannins and their characteristics regarding the main aspects related to their use and possible effects on animal nutrition.