Hydration duration modulates in-vitro protein protection and digestibility in tannin-treated soybean meal

Efficient utilisation of dietary protein improves ruminant performance and reduces nitrogen losses to the environment. Soybean meal (SBM) serves as a major protein source in ruminant nutrition but exhibits high ruminal crude protein (CP) degradability. Tannins reduce ruminal protein degradation, yet the effect of hydration duration during tannin treatment remains poorly defined. In this in-vitro study, we evaluated how three hydration durations (8 h, 16 h, 24 h) combined with chestnut wood extract (CWE) and quebracho wood extract (QUE) tannins at 50 and 100 g/kg influence dry matter (DM) and CP degradability and digestibility of SBM. Hydration duration significantly interacted with tannin treatment for DM degradability and digestibility (p < 0.05). Descriptively, tannin-treated samples showed lower in-vitro CP degradability than the corresponding controls across hydration durations. The lowest CP degradability was observed for CWE at 100 g/kg (380 ± 24.8 g/kg CP) at 8 h hydration, whereas CP digestibility for this treatment was lowest after 16 h hydration and increased to 984 ± 2.8 g/kg CP after 24 h. The highest by-pass CP values were observed after 8 h hydration, ranging from 397 ± 38.9 g/kg CP (QUE 50 g/kg) to 591 ± 25.3 g/kg CP (CWE 100 g/kg). DM degradability decreased by 7% (QUE 100 g/kg at 24 h) to 26% (CWE 100 g/kg at 8 h). These results suggest an 8 h hydration duration may provide the most favourable balance between protein protection and maintained nutrient digestibility.