GROWTH REDUCTION BY DIETARY TANNINS - DIFFERENT EFFECTS DUE TO DIFFERENT TANNINS

The effects of different tannins were compared in feeding trials utili zing rats fed diets that were equal in their total phenolics content. The drug propranolol was used to suppress proline-rich salivary protei n production in some animals in order to examine the defensive potenti al of these proteins against dietary tannins. Differences were evident in the way different tannins affected digestion and the post-digestiv e assimilation of nutrients into new body mass. Different tannins also interacted differently with propranolol and were recovered in fecal m aterial in different quantities. While the two condensed tannin-contai ning diets and one hydrolysable tannin-containing diet each had simila r effects on overall weight gain, they appeared to cause their effects in different ways. These results are discussed in the context of the frequently made assumption that all tannins act as feeding deterrent a llelochemicals in a uniform manner.