Influence of condensed tannin on intake, digestibility, and efficiency of protein utilization in beef steers fed high concentrate diet

This trial was conducted to evaluate if the effect of condensed tannin (CT) is associated with a true protein source on intake, ruminal and total digestibility, ruminal digestion rate, protein efficiency, and microbial efficiency in beef steers fed high concentrate diet (87% of DM). Four Bos indicus steers (407 +/- 12 kg of BW) fitted with rumen cannula were assigned to a 4 x 4 Latin square design, arranged in a 2 x 2 factorial arrangement. Treatments consisted of either inclusion (0.4% of DM) or exclusion of condensed tannin (CT) from quebracho extract (76% of CT) with or without the use of soybean meal (SBM) as source of true protein. The level of inclusion was calculated to provide a daily intake of 1 g/10 kg of BW of CT. Intake of DM and nutrients was not affected (P>0.10) by CT inclusion. However, there was an effect (P<0.10) of CT inclusion on ether extract digestibility. An interaction (P<0.10) was observed between CT and SBM on ruminal digestibility and digestion rate of crude protein (CP): when mixed with soybean meal. CT decreased the ruminal digestibility and, consequently, reduced the digestion rate of CP. Intake of CP increased (P<0.10) with the inclusion of SBM. No differences in DM passage rate were observed (P>0.10) among treatments. Effects of the interaction (P<0.10) between CT and SBM were observed on flux of rumen undegradable protein (RUP), metabolizable protein (MP), and on the ratio MP:CP. In the presence of soybean meal, the addition of CT increased (P<0.10) the flux of RUP and MP, and improved the ratio MP:CP. The yield of microbial protein on the abomasum and the microbial efficiency did not differ among treatments (P> 0.10). There was no difference (P> 0.10) on the pH. VFA, and ruminal ammonia (N-NH3) with the addition of condensed tannin. The N-NH3 increased and the ruminal pH decreased with the inclusion of soybean meal (P<0.10). The utilization of condensed tannin as an additive in beef cattle diets with high level of concentrate and soybean meal as a source of true protein implies positive effects on crude protein utilization, decreasing digestion rate and ruminal digestibility of crude protein and consequently increasing the levels of metabolizable protein, with no changes in the ruminal fermentation parameters. (C) 2011 Elsevier B.V. All rights reserved.