Oil palm fronds are a suitable feed for ruminants. They can replace tropical grasses or roughages such as rice straw (Abu Hassan et al., 1996; Dahlan, 2000). This abundant product is available year-round and can be a satisfactory alternative when the supply of grass or other fodder is a limiting factor (Ishida et al., 1997). It can also be used to minimise grazing time in integrated sheep and oil palm systems (Abu Hassan et al., 1996). When livestock is included in oil palm plantations, oil palm fronds together with palm kernel meal, palm oil mill effluents and leguminous tree forages can provide low-cost and cost-effective balanced ruminant diets for integrated farming systems, resulting in greater animal productivity, greater oil palm yields and increased income (Devendra, 2009).
Oil palm fronds, however, have a high silica and fibre content, are low in protein and have an unbalanced mineral content. These limitations can be overcome by physical and/or mechanical processing, such as immediate chopping, grinding and drying. Other processes include pre-digestion of fibre through chemical and biological treatment and stimulation of rumen microbes by supplementation with energy and protein-rich ingredients (for example with urea and molasses) and supplementation with essential minerals (for example Ca, P and S). The potential of oil palm fronds as a roughage is improved when they are used with a concentrate supplement (Dahlan, 2000).
Empty fruit bunches can also be processed into ruminant feed as pellets but they are rarely used for this purpose (Jalaludin, 1996).
Oil palm fronds are generally quite palatable to ruminants. Good acceptance by cattle, sheep and goats has been observed (Dahlan, 2000). The petioles are unpalatable to goats (Islam et al., 2000b).
Dry matter and organic matter digestibility of fresh, dried and ensiled oil palm fronds is low, in the 40-55% range (Dahlan et al., 2000; Abu Hassan et al., 1996; Kawamoto et al., 2001; Islam et al., 2000b). Estimated energy values are poor with a ME about 4.9 to 6.5 MJ/kg DM (Dahlan, 2000).
Digestibility and intake can be improved through processing. In an experiment where goats were given oil palm fronds as the sole feed, ensiling slightly increased OM digestibility while pelleting significantly increased intake. However, intake and digestibility were the highest when the animals were given a complete diet containing 50% of oil palm fronds, 15% palm kernel meal and other sources of energy (molasses) and nitrogen (fish meal and urea) (Dahlan et al., 2000). In another experiment using oil palm fronds in mixed diets, pelleted fronds were the least digestible (25%) but gave the best intake. NaOH treatment resulted in a more digestible product (more than 50%) but was detrimental to palatability (Kawamoto et al., 2001). Steaming under moderate or low pressure (such as 10 kg/cm² for 20 min followed by oven-drying at 60°C for 48 h) significantly improved nutrient degradability (Bengaly et al., 2000 cited by Paengkoum et al., 2006a).
In goats, urea treatment (3 and 6% DM) had a negative effect on digestibility (Abu Hassan et al., 1996) but the addition of up to 3 g/kg of urea to steamed-treated oil palm fronds increased intake and digestibility (Paengkoum et al., 2006a). In sheep, urea treatment of steam-treated oil palm fronds was found beneficial to intake and digestibility up to 16 g/kg (Bengaly et al., 2010).
Oil palm fronds can support an efficient rumen function in terms of NH3-N concentration when 50% or more is used in the diet, but the latter requires additional fermentable N (Islam et al., 2000a).
Cows fed 30% oil palm fronds silage and 70% palm kernel-based concentrate produced more milk than those fed 50% oil fronds or 50% grass. No adverse effect on milk flavour was observed. Proposed optimal inclusion levels for dairy cattle vary between 30% (Abu Hassan et al., 1996) and 55% (diet DM) (Dahlan, 2000).
In feeding trials with bulls, the inclusion of high amounts of oil palm silage (with or without urea treatment) combined with a palm kernel meal-based concentrate decreased carcass fat but was also detrimental to weight gain and lean meat production. However, inclusion of up to 30% oil palm silage (that resulted in a 620 g/day average daily gain) was considered to be economically viable due to the low cost of the product (Abu Hassan et al., 1996). Other authors have proposed a higher optimal inclusion of 55% (diet DM) (Dahlan, 2000).
Oil palm frond silage was found to be a satisfactory roughage for buffaloes when included as a part of the diet based on palm kernel meal or sago meal (Metroxylon sagu). Frond silage included as 30% of the diet resulted in a 470 g/d average daily gain (Abu Hassan et al., 1996; Dahlan, 2000).
Lambs fed 30% oil palm frond silage with 70% concentrates grew faster than the control group on pasture (79-82 g/day) (Schrader, 1994 cited by Dahlan, 2000).
Oil palm fronds have been found suitable to be used as a maintenance feed and to produce quality meat from goats (Dahlan, 2000). Proposed optimal inclusion levels for goats vary between 30% (Abu Hassan et al., 1996) and 50% (diet DM) (Dahlan, 2000).