RESUMEN
Ammoniation of oil palm frond (OPF) with non-protein nitrogen (N) sources has been shown to improve the nutritional value and digestibility of OPF in ruminants. This study evaluated the effect of treating OPF without (control) or with different urea levels (1%-5%) on chemical composition and in vitro gas production, digestibility and fermentation properties using goat rumen fluids. The results showed that the treated OPF with urea (1%-5%) had significantly lower (p < 0.05) dry matter (DM), organic matter (OM) and ash contents than that of the control. The crude protein (CP) content of treated OPF increased (linear p < 0.05; quadratic p < 0.05) with increasing levels of urea inclusion (1%-5%), whereas the contents of neutral detergent fibre (NDF) and acid detergent lignin (ADL) were significantly (p < 0.05) decreased. The CH4 (ml/500 mg DM incubated) production decreased (linear p < 0.05) with increasing levels of urea inclusion in treated OPF silage. However, in vitro DM and OM degradability were significantly (p < 0.05) increased by higher inclusion levels of urea (4% and 5%). OPF treated with 4% or 5% urea also revealed significantly (p < 0.05) higher total volatile fatty acids and ammonia-N than the control and OPFs treated with 1%-3% urea. Ammoniation of OPF with urea improved its nutritional value and in vitro rumen fermentation profiles in goats. The impact was more pronounced for 4% or 5% urea-treated OPF.