The use of a tannin crude extract from Cistus ladanifer L. to protect soya-bean protein from degradation in the rumen

Cistus ladanifer L. (CL) is a perennial shrub abundant in dry woods and dry land of Mediterranean zone, with high level of tannins. Tannins bind to protein, preventing its degradation in the digestive compartments. This tannin/protein complex may be advantageous when partially protecting good-quality feed protein from excessive rumen protein degradation. The objective of this trial was to use a CL phenol crude extract to prevent excessive rumen degradation of soya-bean meal protein. The phenolic compounds were extracted using an acetone/water solution (70:30, v/v). Soya-bean meal was then treated with this crude CL extract, containing 640 g of total phenols (TP) per kg of dry matter (DM), in order to obtain mixtures with 0, 12.5, 25, 50, 100 and 150 g of TP per kg DM. Three rumen-cannulated rams were used to assess in sacco rumen degradability of DM and nitrogen (N). The three-step in vitro procedure was used to determine intestinal digestibility. Increasing extract concentrations quadratically decreased the N-soluble fraction a ( R 2¼ 0.96, P¼ 0.0001) and increased the non-soluble degradable fraction b ( R 2¼ 0.92, P¼ 0.005). The rate of degradation c linearly decreased with CL extract doses ( R 2¼ 0.44, P¼ 0.0065). For the effective rumen degradability of N, a linear reduction ( R 2¼ 0.94, P , 0.0001) was observed. The in vitro intestinal digestibility of protein (ivID) quadratically decreased ( R 2¼ 0.99, P , 0.0001) with TP inclusion and the rumen undegradable protein (RUP) showed a quadratic increase ( R 2¼ 0.94, P¼ 0.0417). Total intestinal protein availability, computed from the RUP and ivID, linearly decreased with TP inclusion level ( R 2¼ 0.45, P¼ 0.0033).