The purpose of this paper was to show that a high polyphenolic compound content in the sorghum grain (Sorghum saccharatum, var sugar drip) has an unfavorable influence on the nitrogen absorption. In order to arrive at this conclusion, the tannin content in sorghum flour was reduced by means of a treatment with polyvinylpyrrolidone (PVP) as a complexing agent. Several biological experiments were performed with non-treated flour (S) and with PVP-treated flour (S + PVP). Treatment improved true digestibility (D), having obtained the following values: for S = 31 +/- 2.67, and for S + PVP = 55.8 +/- 3.48 (significance P less than 0.001). The tannin evaluation yielded the following results: S = 1.90 g/100 g, and S + PVP = 0.85 g/100 g reported as tannic acid. The digestibility increase induced a better nitrogenous utilization, the net protein utilization (NPU) values being from 19 +/- 1.58 to 37 +/- 3.36 for S, and S + PVP, respectively.