Tannin-binding properties are concentration dependent. Hydrogen bonds and hydrophobic interactions are the main forces involved in binding. The proline content of proteins is very important. There are some beneficial nutritional effects for ruminants eating moderate amounts of tannins. A higher nitrogen retention, i.e., less nitrogen loss by urine, which could compensate for lower digestibility .
Tannins can protect proteins against degradation by rumen microbes.
However, the tannin released must not be harmful to gastric and gut tissues or decrease intestinal absorption via complexation with enzymes. Some authors argue that since there should be less protein degradation in the rumen, the consequence should be lower rumen ammonia concentration. In addition, nitrogen would recycle faster in response to increased saliva production. The increased saliva flow could also cause increased rumen escape of dietary protein, which is good. However, the current analytical tools are not sufficient accurate or present technical problems to prove the last two arguments.