Detoxication of Dietary Tannic Acid by Chicks

In an effort to learn more about the mechanism for detoxication of dietary tannins in aves, tannic (digallic) acid (TA) was fed to young chicks at 0.5 and 1.0% of their diet together with supplemental methionine (as the hydroxy analogue, Ca salt) (MHA), choline, betaine, arginine and ornithine individually and in various combinations. In the absence of these nutrients, TA depressed the growth rate of chicks and the depression increased in severity with the level added and with duration of the feeding period. The TA-induced growth depression was partially alleviated by supplementing the diet singly with MHA or choline and to a lesser extent with arginine. The combination of MHA, choline (or betaine) and arginine (or ornithine) further reduced the ill effects of TA fed at the 1% level and completely remitted the effects of TA fed at the 0.5% level. With suboptimal levels of methionine, and in the absence of dietary TA, increasing increments of arginine depressed growth linearly. This was corrected when sufficient MHA was added. When TA was fed with suboptimal levels of methionine, the supplemental arginine had no effect on growth rate; but when MHA was added to the TA diet, supplemental arginine improved the growth rate, resulting in a significant reduction in toxicity of TA.