Utilization of Steam-treated Oil Palm Fronds in Growing Saanen Goats: II. Supplementation with Energy and Urea

The objective of this study was to evaluate the effect of protein and energy on goats fed oil palm fronds (OPF) as roughages.Twenty-four male Saanen goats aged between 7 and 8 months and weighing 23.4±1.6 kg were used in a 2×3 factorial design.Factors were three levels of urea (3%, 4% or 5%) and two levels of energy (low energy (LE) or high energy (HE)).On average, all parameters measured, including dry matter intake (DMI), nutrient digestibility, digestible nutrient intakes, ruminal ammonia-N (NH 3 -N), ruminal total volatile fatty acid (total VFA) and individual VFA concentrations (mM/L), microbial N supply, P/E ratio and N retention were higher for HE compared to LE diets.Significant (p<0.05)interactions were found between levels of urea and energy for nonstructural carbohydrate (NSC) and energy (DE) digestibilities, ruminal NH 3 -N and total VFA concentrations.HE diets had higher N absorption and retention than LE diets.Interactions between urea and energy for plasma urea nitrogen (PUN), heat production (HP), and urine and faeces N excretion were significantly lower (p<0.05)for the HE diets than those recorded for the LE diets.The results indicated that supplementation of energy enhanced utilization of urea and resulted in higher animal performance as a consequence of improved ruminal fermentation, microbial yield and N balance.However, the optimal level of urea supplementation remained at 3% in the HE diet.