Assessment of the nutritive value of urea–calcium hydroxide-treated rice straw by in sacco technique

The objective of the present study was to determine the effect of urea–lime treatment on nutritive value and rumen degradability of rice straw by using the nylon-bag technique. Straw was assigned to treatments according to a 2 × 3 × 5 factorial arrangement in a completely randomised design. Factor A comprised two storage times (10 and 20 days), Factor B comprised three levels of lime addition (0%, 1% and 2%) and Factor C comprised five levels of urea treatment (1%, 2%, 3%, 4% and 5%). Two ruminal fistulated beef steers (410 ± 10 kg) were used to determine in situ DM degradability. The results showed that increasing the urea treatment level increased crude protein and organic matter concentrations, while concentrations of neutral detergent fibre and acid detergent fibre decreased linearly with an increasing lime treatment level (P < 0.05). Moreover, urea and lime treatment increased the soluble fractions at time zero (a), insoluble degradability fractions (b), rate of degradation (c), potential degradability (a+b) and the effective degradability of DM (P < 0.05). Furthermore, rice-straw treatment at 20 days showed a better straw chemical composition and rumen degradability (P < 0.05) than that at 10 days. In conclusion, treatment with urea and lime improved the quality and ruminal degradability of rice straw. The present study suggested that urea treatment can improve the nutritional value of rice straw, especially, treatment with 3% urea together with 2% lime.