Two experiments were undertaken using lambs and cows fed steam-treated oil palm frond (SOPF). In the first experiment, 8 lambs received SOPF supplemented with 4 levels of urea: 0 (U0), 8 (U8), 16 (U16) and 24 g urea/kg SOPF (U24) in a replicated 4 x 4 Latin square design. When the lambs were given the above diets, all the measurements for intake and digestibility (dry matter, organic matter and nitrogen) increased in a linear (P < 0.001) manner up to the level of U16, except for intake of nitrogen (N); no further benefits were obtained when more urea was added. Giving 16 g urea per kg could provide sufficient fermentable N for SOPF utilization. Three ruminally cannulated non lactating cross-bred Charolais x Kedah-Kelantan cattle were used in the second experiment to determine the effective degradability of N from cassava foliage (CF), cassava leaves (CL) and soybean meal (SM) suspended in the rumen. The animals were fed with amount of dry matter (DM) that was equivalent to 1.5% of body weight of SOPF supplemented with 16 g of urea per kg. The effective degradability of N from CF, CL and SM was calculated from their residues after incubation in the rumen for 2, 4, 8, 16 and 24 h. Increasing the rate of outflow of particulate matter (from 2, 5 to 8%/ h) from the rumen, resulted in a greater disappearance of N (P < 0.05) from CF than from CL or SM. Because of its relative faster rate of degradation, CF in addition to the provision of fermentable N may also contribute easily degradable cellulose and hemicellulose to SOPF-based diets. The nylon bag technique appeared to be a powerful tool for screening protein supplements.
Key words: Degradability, nitrogen, oil palm frond, ruminant, steam treatment, supplementation.
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