Effects of Tannins on Conjugated Linoleic Acids (CLA) Accumulation in Ruminant Products

Conjugated linoleic acid (CLA) is considered to be of high importance for human health that exerts important physiological effects, including anticarcinogenic effects, prevention of cholesterol-induced atherosclerosis, enhancement of the immune response, reduction in fat accumulation in body, ability to enhance growth promotion, antidiabetic effects and improvement in bone mineralization. CLA requirement for human should more than 400 mg/d for good health. The predominant CLA in ruminant fats is the cis-9, trans-11 CLA isomer, which accounts for more than 80% of total CLA isomers in dairy products and 75% of those in beef fats. The presence of CLA in ruminant products relates to the biohydrogenation of unsaturated fatty acids by rumen bacteria. The CLA concentrations in ruminant products can be increased by nutritional and management practices that facilitate higher fore-stomach output of CLAs and vaccenic acid (trans-11 C18 : 1) for absorption and incorporated into animal tissues. The ability of plant extracts including tannins to modify the fatty acid composition of ruminant products has received great attention recently. There is very limited information pertaining to the effects of tannins on ruminal biohydrogenation process and CLA content in milk and meat. The condensed tannins have been shown to inhibit the growth of many ruminal bacteria including bacteria associated with ruminal biohydrogenation. It has been reported that the terminal step of ruminal biohydrogenation process was inhibited by condensed tannins, thus leading to an accumulation of vaccenic acid in ruminants’s tissue. This selective activity of tannins to rumen bacteria could be beneficial nutritionally by altering the ruminal biohydrogenation process and hence enhancing CLA content of ruminant-derived products. Keywords: condensed tannin, Conjugated linoleic acid, biohydrogenation, Meat CLA, Milk CLA