Scienceline Publications Online Journal of Animal and Feed Research 2228-7701 6 2 2016 March EFFECT OF DIETARY TANNIN SOURCE FEEDS ON RUMINAL FERMENTATION AND PRODUCTION OF CATTLE; A REVIEW 45 56 http://www.ojafr.ir/main/attachments/article/120/Online%20J.%20Anim.%20Feed%20Res.,%206(2)%2045-56,%202016.pdf EN Shewangzaw ADDISU University of Gondar, Department of Animal Production and Extension, P.O.Box, 196 Gondar, Ethiopia Generally, tannins are widely distributed throughout the plant kingdom, especially among trees, shrubs and herbaceous leguminous plants. Tannins are naturally occurring polyphenols with different molecular weights and complexity that are synthesized during the secondary metabolism of plants. Tannins might bind to macromolecules (proteins, structural carbohydrates and starch) and decrease their availability to digestion. Tannins based on their chemical structure and properties divided into two groups, hydrolyzable tannins (HT) and Condensed tannins (CT, proanthocyanidins). Tannins are polyphenols, which directly or indirectly affect intake and digestion. They are the primary source of astringency in plants, which results from binding to proteins, forming soluble or insoluble complexes. The nature of the interaction is greatly dependent on the structure of the polyphenols and the proteins involved. Relatively low concentration of tannins (0.5% of DM intake) is sufficient to destabilize the bloat proteins while high concentration (2-4% of DM intake) is needed for improvement of protein utilization. High concentration (> 5% of dry weight reduces feed intake and feed conversion efficiency. Tannins containing forages will be important for small ruminants to control of gastrointestinal parasites. Animals fed condensed tannin had lower dressing percent than controlled one; with dressing percent being intermediate for animals fed hydrolysable tannin. Neither tannin source affected the animal’s consumption of the diet or the animal’s growth. Additionally, the tannin sources did not affect the meat or by-product tissues, making tannin supplementation a viable option in finishing beef cattle. Therefore, tannin source feed will have its own advantages and disadvantages on animals’ performance. Dietary Tannin Digestion Ruminal fermentation