Chapter 4: African oil palm

The African oil palm, Elaeis guineensis (Jacq.), is characterized by its vertical trunk and the feathery nature of its leaves. Every year, 20 to 25 new leaves, called "fronds", develop in continuous whorls at the apex of the trunk. The fruit bunches develop between the trunk and the base of the new fronds. Although new plantations start to bear at three years, generally the first commercial crop requires between five and six years and continues to produce for 25-30 years, or until the palms grow too high to be harvested. Once a plantation reaches full production, a new inflorescence is produced every 15 days. It weighs between 15 and 20 kg and can contain up to 1500 individual palm fruits of between 8 to 10 grammes each. The individual fruits consist of the following four parts:

a pericarp, a thin outer skin, which upon ripening changes from brown to orange;a mesocarp, a layer of fibrous material, which surrounds the nut;an endocarp or hard inner shell (nut) to protect the seed or kernel, andthe seed (kernel).

PRODUCTION AND TECHNOLOGICAL PROCESS

Production

The African oil palm, which yields about 20t/ha/yr of fresh fruit bunches (Bolaños, 1986; Espinal, 1986: Garza, 1986), is capable of producing between three to five t/ha of crude oil from the fruit (mesocarp) and an additional 0.6 to 1.0 t/ha from the palm kernels (Ocampo et al., 1990a). Its productivity is influenced by climate, soil type, genetic factors, maturity, rainfall, fertilization and the harvest period. Mijares (1985) has stated that for optimum annual production the African oil palm requires a minimum of 1600 mm of well distributed precipitation, a relative humidity no less than 75%, a minimum and maximum temperature of between 17 and 28 C., a total of 2000 hours of light and a soil depth of 100 centimetres.

There are two distinct types of oil palm: the "dura" and the "pisifera". The basic difference has to do with the inner nut. The nut of the dura type of oil palm has a thick and hard shell while the pisifera type has a small kernel, with no shell, but rather surrounded by a matrix of fibre. When a pisifera male is crossed with a dura female, a "tenera" type of fruit is produced; its shell is of intermediate thickness. Currently, it is this type of oil palm that is most widely grown in plantations.

The African oil palm produces two main commercial products: raw or crude oil, approximately 22% of the weight of the fresh fruit bunch, and the palm nuts which represent 4-6%. When the nut is processed, it yields palm kernel oil and palm kernel meal (Figure 4.1). The two main industrial residues, the oil-rich fibrous residue and the palm nut shells, are used as sources of energy to run the factory. The empty fruit bunch is normally incinerated and the ash is returned to the plantation as fertilizer.

The initial interest in the African oil palm as a feed resource for pigs was in the extracted and non-extracted palm kernel meal. This was because when nuts of the oil palm were first brought to Europe from Africa as ship's ballast, they were jettisoned into the sea before the ships were reloaded. However, soon the oil millers recognized their value and began processing them for oil in order to supplement copra oil in the manufacture of soap, paints and for other industrial applications (Collingwood, 1958). The meal was used as a major protein supplement for pigs and cattle until soya bean meal became commercially available.

Oil palm cultivation started at the beginning of this century (Devendra, 1977). By 1980, production of oil had risen to slightly more than five million tons and, by 1992, annual world production reached thirteen million tons. As seen in Table 4.1, the primary areas of production are Southeast Asia, followed by the west coast of Africa and Latin America. Currently, Malaysia produces half the world's production of palm oil, followed by Indonesia and Nigeria. Presently, the fourth and fastest growing producer of palm oil is Colombia, where production has more than quadrupled in 12 years. In that country, (Ocampo et al., 1990b) has reported that the average annual production of fruit is 15 t/ha of which raw oil represents slightly more than three tons.

Table 4.1. Production of African palm oil: world, regional and top four countries, tonnes (FAO, 1992).

Geographical area 1979-81 1992
World 5 046 308 12 725 346
Africa 1 337 913 1 835 888
Nigeria 666 667 900 000
Latin America 190 780 753 251
Colombia 70 500 304 496
Asia + Oceania 3 502 851 10 136 207
Indonesia 720 826 3 162 228
Malaysia 2 528 947 6 373 461

TECHNOLOGICAL PROCESS

The technological process by which the oil is extracted from the palm fruit consists of the following steps; note that the fresh fruit bunch includes the stem and the adhering individual palm fruits.

Reception: where sand, dirt and gravel are separated from the fresh fruit bunch.

Sterilization: necessary to rapidly inactivate certain enzymes which tend to reduce the quality of the oil by increasing the amount of free fatty acids. In addition, this process contributes to the mechanical separation of the fruit from the stem and to the rupture of the oil cells within the mesocarp.

Oil extraction: An oil press, into which hot water is injected, is used to separate the crude oil from the solid or fibrous-like material containing the nuts. The crude oil is then pumped to the purification section.

Figure 4.1 shows the quantities of the principal components of the oil palm based on 100 tons of the fresh fruit bunch. The nuts are treated and cracked to extract the kernel which contains approximately 50% oil. The oil-rich fibrous residue, traditionally used as a source of energy to run the plant, has a caloric value superior to 18.8 MJ/kg. This is largely due to the residual oil, calculated as between 8 and 18 percent (Brezing, 1986; Solano, 1986; Wambeck, 1990).

Similar to the proposal for livestock diversification within the sugar industry (FAO, 1988), the integration of pig production within the oil palm industry might introduce a certain degree of flexibility in the entire enterprise, resulting in: an increase in the productive capacity of the plant, particularly during the period of maximum industrial yield; a significant reduction in plant maintenance; increased employment opportunities related to the utilization of the different byproducts for livestock feeding; the production of animal wastes and thereby organic fertilizer for the plantations and, perhaps most importantly, an overall reduction in the amount and/or concentration of the industrial effluents which threaten the contamination of the surrounding ecosystem (Ocampo, personal communication).

As a follow-up to these observations, the following information summarizes the average daily amount of products and sub-products produced in a oil palm processing plant of 125 t/day and 10t/hour (Table 4.2).

One factor that might require attention if derivatives from the African oil palm present new opportunities to be used as energy feed resources for pigs is the cyclic nature of its production. Bolaños (1986) has reported that in Costa Rica the average monthly yield of fresh fruit bunch can vary from 6% during the dry winter months to 10 or 12% during the rainy, summer season. In that country, the annual yield of the fresh fruit bunch is 20 t/ha and with the oil-rich fibrous residue representing 12% of this amount, this could mean the production of 0.3 t/ha of oil-rich fibrous residue during the wet season as opposed to only 0.15 t/ha during the dry or winter season.

Figure 4.1. Production technology for 100 t of fresh fruit bunch of African oil palm (Solano 1986).

Table 4.2. Potential feed resources in an African oil palm processing plant, air-dry basis.

t/day t/year t/ha/yr
Fresh Fruit Bunch 125 25000 20
Palm oil 25 5000 4
Palm kernel meal 2.5 1000 0.8
Empty Fruit Stem 40 8000 6.4
Ash (from stem) 0.6 125 0.1
Effluent 80 16000 13
Oil-rich fibrous residue 13.7 2750 2.2
Shell (from kernel) 12 2500 2
Ash (from shell) 0.6 16000 13

Source: Brezing (1986)

However, if sugar cane, generally harvested only in the dry season, was integrated into this feeding system, the two energy feed resources might complement each other. The data in Tables 4.6 and 4.7 tend to support this interesting concept.

USE FOR PIGS

As earlier mentioned, one of the first references to the use of derivatives of the oil palm for pigs referred to the use of the extracted and non-extracted palm kernel meal in complete, dry rations for growing/finishing pigs. Most pig farmers contended that the gritty texture of the meal affected consumption, and therefore performance. However, palm kernel meal continued to be used for many years as a replacement for scarce cereals, mainly because it was available, relatively inexpensive and highly nutritious (Crowther, 1916, cited by Collingwood, 1958). In the 1930s, when a commercial process for extracting oil from the soya bean was perfected and it was seen that a higher quality animal protein supplement (soya bean meal), would be commercially available, the byproduct from the extraction of the oil from the kernel, palm kernel meal, was destined for ruminants (PNI, 1990). Currently, palm kernel meal represents about one per cent of world trade in oil seed meals. Table 4.3 gives the chemical composition of several oil palm byproducts.

Table 4.3. Chemical composition of African oil palm byproducts.

Component Oil-rich fibrous residue a (% DM) Dry sludge a (% DM) Fresh centrifuged sludge solids b (% AD)
Dry matter 86.2 90.3d 15.0-20.8
Crude protein 4.0 9.6 3.1-3.4
Crude fibre 36.4 11.5 3.0-5.2
Ether extract 21.0 21.3 2.4-3.5
Ash 9.0 11.1 2.8-3.4
Nitrogen free extract 29.6 46.5 -
Calcium 0.31 0.28 -
Phosphorous 0.13 0.26 -
Gross energy (MJ/kg) 18.1 18.7 -

Sources: a Devendra (1977); b Ong (1982)

To date, derivatives of the African oil palm have shown potential feeding value for pigs in conventional, cereal-based rations: the de-hydrated palm oil mill effluent and the fresh centrifuged sludge solids have been studied both by Devendra et al. (1981) and by Ong (1982), and the whole palm nut by Flores (1989) and Chavez (1990). However, recent interest has focused on the use of primary products and by-products of the African oil palm as a partial or complete energy source replacement in swine rations, particularly where the protein is offered separately, in the form of a restricted amount of a high-quality supplement. It has been shown that the oil-rich fibrous residue (ORFR), normally used as a source of energy to run the factory, can also furnish the necessary energy for the pig (Ocampo et al., 1990a, 1990b). As exemplified in following sections, the successful experimental use of the crude oil (Ocampo, 1994b), combinations of the crude oil and sugar cane juice (Ngoan and Sarría, 1994) and even the whole fresh palm fruit (Ocampo, 1994a, b) further emphasize the fact that other oil palm byproducts can serve to completely replace cereals in rations for swine.

Crude (raw) palm oil

Crude palm oil has traditionally been used up to about 5% in dry diets for pigs in a manner similar to molasses: to improve palatability, to reduce dustiness, to supply vitamins and to improve the texture of rations prior to pelleting (Devendra, 1977; Hutagalung and Mahyudin, 1981). The oil contains approximately 80% of unsaturated fatty acids (Table 4.4) and 10% of linoleic acid, an essential fatty acid required at a dietary level of 0.1% for pigs (NRC, 1988).

Table 4.4. Composition of the fatty acids in the oil from fruit and kernel of the African oil palm (% AD).

Fatty acids Palm oil Palm kernel oil
Myristic 1.6 -
Palmitic 45.3 7.8
Stearic 5.1 2.5
Oleic 38.7 12.6
Linoleic 9.2 1.7
Lauric - 15.7
Capric - 47.3
Caprilic - 4.1
Caprolic - 4.3

Source:Pardo and Moreno (1971), cited by Ocampo et al. (1990b)

The addition of from 2 to 10% of crude palm oil in the diets of growing pigs was studied by Fetuga et al. (1975) who found no significant effect on performance. When palm oil was compared to groundnut oil, lard or beef tallow, there were no significant growth differences, however, increasing the level of palm oil in the diet slightly increased the percentage of lean cuts (Babatunde et al., 1971, 1974, cited by Devendra, 1977). This same observation was reported by Balogun et al. (1983) cited by Ngoan and Sarría (1994) who noted that the addition of 30, 64 or 97 g/kg of palm oil to the ration increasingly improved muscle development.

In Malaysia, it was reported that six groups of pigs from 16 to 81 kg were fed iso-nitrogenous diets containing different levels of palm oil, from 5 to 30 percent. Although the results were reported as not significant, the average daily gains obtained on the experimental diets were 10% superior compared to that of the cereal control; in addition, where palm oil was included, the conversions were improved by an average of 17 percent (Devendra and Hew, cited by Devendra, 1977).

Recently, Ocampo (1994b) showed that palm oil and a source of protein, either fortified soya bean meal and rice polishings, or combinations of fortified soya bean meal/fresh Azolla and rice polishings, might provide an interesting feeding system for the production of pigs in the tropics, particularly if the pigs were integrated with the palm plantations. Pigs of an initial average liveweight of 30 kg were fed diets in which 10, 20 and 30% of the protein from fortified soya meal was replaced by fresh Azolla filiculoides, a water fern (Table 4.5).

Table 4.5. Composition of diets using crude palm oil, rice polishings and fresh Azolla filiculoides as a replacement for the protein in soya bean meal (kg AD/day).

% replacement of protein in soya bean meal by Azolla
growing phase: 30-60 kg finishing phase: 60-90 kg
0 10 20 30 0 10 20 30
Protein supplement 0.50 0.45 0.40 0.35 0.50 0.45 0.40 0.35
Rice polishings 0.10 0.10 0.10 0.10 0.15 0.15 0.15 0.15
Crude palm oil 0.50 0.50 0.50 0.50 0.80 0.80 0.80 0.80
Fresh Azolla 0.0 1.74 3.48 5.21 0.0 1.74 3.48 5.21

Source: Ocampo (1994b); * contains: soya bean meal, 86%; dicalcium phosphate, 10%; salt, 2% and a vitamin/mineral premix, 2%

In the morning, the pigs were fed the daily ration of protein supplement and rice polishings, and half the daily allowance of oil and Azolla. In the afternoon, they received the remaining portion of Azolla and oil. The average daily gain (g) and dry matter feed conversion for the control treatment, without Azolla, and the groups where 10, 20 and 30% of the protein in soya bean meal was replaced by that of Azolla were: 526, 2.10; 561, 1.98; 535, 2.00 and 452, 2.20, respectively.

In the same publication reference was made to a commercial piggery that used the following "palm oil feeding system". For that, a total of 170 growing/finishing pigs, in 4 groups, were fed daily one kilogramme of protein supplement and 0.5 kg of crude palm oil. The protein supplement contained: 450 g soya bean meal, 374 g palm kernel meal, 150 g rice polishings, 20 g dicalcium phosphate and 3 g each of salt and a vitamin/mineral premix. The initial average liveweight (kg), average daily gain (g) and dry matter feed conversion for each of the 4 groups were 32.0, 722, 1.80; 24.2, 628, 2.00; 25.8, 524, 2.40 and 26.0, 464, 2.80, respectively. In spite of the fact that the diet was the same for all groups, no explanation was offered for the observed variation in performance, inferring, perhaps, that the "palm oil feeding system" requires further refinement.

Palm oil has also been studied as either a partial or complete energy source replacement for pigs, also fed fresh sugar cane juice and a restricted protein supplement. The oil replaced 25, 50, 75 and 100% of the energy in cane juice in both the growing and finishing phases of this most interesting and unique feeding system to study the potential integration of sugar cane and the African oil palm as dry/wet-season energy feed resource alternatives for pig production in the tropics (Table 4.6).

The average daily gain was not significantly affected by treatment in the growing phase, however, during the finishing phase, gains were significantly lowered when palm oil replaced 75 and 100% of the juice (Table 4.7). In both phases, the average daily feed intake was lower for those pigs fed palm oil which according to the authors, might have been related to its low palatability or high energy content. They reported a digestible energy value for palm oil and sugar cane juice in pigs as 37.5 and 14.5 MJ/kg of DM, respectively. Feed conversions were significantly improved by the addition of palm oil. Carcass measurements were not affected.

Table 4.6. Replacement of the energy in sugar cane juice (SCJ) by that in palm oil (PO) for growing/finishing pigs (kg AD/day). *

Liveweight, kg <30 40 50 60 70 80 90 >90
100 SCJ 6.0 7.5 8.5 9.5 10.5 11.5 13.0 >14
75 PO/25 SCJ 4.5/.1 6.0/.15 7.0/.2 8.0/.2 9.0/.25 10/.25 11.0/.3 12.0/.3
50 PO/50 SCJ 3.0/.2 4.0/.3 4.5/.35 5.0/.4 5.5/.45 6.0/.5 6.5/.55 7.0/.6
25 PO/75 SCJ 1.5/.3 2.0/.45 2.5/.5 2.5/.6 3.0/.65 3.0/.75 3.5/.8 3.5/.9
100 PO 0.4 0.6 0.7 0.8 0.9 1.0 1.1 1.2

Source: Ngoan and Sarría (1994); * plus 500 g/d of a 40% crude protein supplement

Table 4.7. Performance of finishing pigs (50-90 kg) fed a restricted protein supplement (RPS)* with energy from sugar cane juice (SCJ) increasingly replaced by palm oil (PO).

100 SCJ 75 SCJ 25 PO 50 SCJ 50 PO 25 SCJ 75 PO 100 PO
Initial liveweight, kg 51.1 50.1 48.9 50.2 45.2
Final liveweight, kg 99.5 93.7 91.2 89.8 84.2
ADG, g 768 693 672 628 615
DM feed intake, kg/d 3.05 2.32 2.14 1.77 0.92
DM feed conversion 3.97 3.35 3.18 2.82 1.47

Source: Ngoan and Sarría (1994); Ngoan (1994); *The RPS was 500g/day of 91% soya bean meal, 6% minerals, 1% salt and 2% of a vitamin premix

Oil-rich fibrous residue (ORFR)

The residue which remains after the crude oil is separated from the sterilized fruit by means of a screw-press, represents approximately 12 to 15% of the fresh fruit bunch. The chemical composition of this residue is presented in Table 4.3. This material, reported to contain from 63% (Wambeck, 1990) to 70 or 85% dry matter (Solano, 1986) still contains from 6 to 8% of residual oil. It is of a deep yellow-tangerine color, with a fibrous consistency, sweetish smell and greasy-like texture (Ocampo et al., 1990a). It is used as the main source of energy to run the plant.

ORFR has been studied as a complete replacement for the energy derived from cereals. Diets in which sorghum was the sole energy source, or where 25, 50, 75 or 100% of the energy from sorghum was replaced by this residue, were offered ad libitum to pigs from 20 to 90 kg, also fed a restricted amount of fortified soya bean meal to meet the current, daily, NRC (1988) requirement for crude protein (Ocampo et al., 1990a). Preliminary results showed that pigs can grow extremely well on this type of feeding system. Where ORFR replaced 100% of the energy supplied by sorghum, the average liveweight growth was 639 g/day. The pigs consumed a daily average of 0.75 kg of protein supplement together with 2.32 kg of oil-rich fibrous residue (Table 4.8).

Table 4.8. Oil-rich fibrous residue as a partial or complete replacement for the energy in sorghum for pigs (20-90 kg).

0% ORFR 25% ORFR 50% ORFR 75% ORFR 100%ORFR *
Initial liveweight, kg 19.8 20.6 21.7 22.2 22.6
Final liveweight, kg 89.7 91.1 92.5 92.6 94.2
Days to finish 133 119 112 112 112
ADG, g 525 592 632 629 639
DM feed intake, kg/d 2.1 2.1 2.2 2.3 2.8
DM feed conversion 4.00 3.59 3.49 3.75 4.47

Source:Ocampo et al. (1990a); * fed 0.55, 0.64 and 0.9 kg/day of fortified soya bean meal (see Table 4.5) during the 3 phases of: weaners, growers and finishers, respectively

Following this initial trial, Ocampo et al. (1990b), attempted to prove an observation of Sarría et al. (1990), that when pigs are fed a restricted amount of a high quality protein supplement, particularly when the required levels of essential amino acids are supplied by soya bean meal, lower amounts of total crude protein are feasible. This amounts to approximately 200 g/day and can be provided in 500 g/day of a 40% protein, soya bean meal-based supplement. The concept had been first developed through feeding systems based on sugar cane juice (see Chapter 3).

For this study, the basic diet was ORFR, fed ad libitum. Three groups of growing/finishing pigs were fed constant amounts (high, medium or low) of fortified soya bean meal throughout the entire experimental period. A fourth group, the control, received different amounts of fortified soya bean meal (high, medium and low) to correspond with the needs of each of the three developmental phases: weaners, growers and finishers (Table 4.9). The authors concluded that the two groups that received the least amount of protein exhibited an inferior performance but gave the highest economic returns. A more recent trial studied the effect of supplementing this unusual feeding system (ad libitum ORFR and a restricted amount of protein supplement) with methionine and/or B-complex vitamins (Ocampo, 1992). None of the experimental treatments produced significant results.

Table 4.9. Different amounts of restricted protein supplement (RPS) * and free-choice oil-rich fibrous residue for pigs from 22 to 90 kg.

Control ** High (0.64 kg/d) Medium (0.57 kg/d ) Low (0.50 kg/d)
Initial liveweight, kg 22.7 22.8 22.8 22.1
Final liveweight, kg 90.2 90.0 90.4 90.3
Days to finish 121 126 124 135
ADG, g 558 532 545 505
AD feed intake, kg/d: RPS

        ORFR

0.70

2.33

0.64

2.44

0.57

2.22

0.50

2.56

DM feed conversion 4.80 5.20 4.60 5.40

Source: Ocampo et al. (1990b); * see Table 4.5; ** 0.50, 0.64 and 0.90 kg/day of RPS fed during three consecutive 40-day periods: weaners, growers and finishers.

Palm oil mill effluent and palm oil sludge

The palm oil mill effluent, the final liquid discharge after extracting the oil from the fresh fruit bunch, contains soil particles, residual oils and suspended solids but only 5% of dry matter. While Wambeck (1990) stated that it represents 0.5 t/t of fresh fruit and can cause serious problems to the entire surrounding ecosystem, Brezing (1986) went one step further and estimated that a processing plant with a capacity of 10 tons fresh fruit per hour would require a water treatment plant comparable to that required by a population of half a million inhabitants!

Palm oil sludge is the material that remains after decanting the palm oil mill effluent (Devendra et al., 1981). It can be either filter-pressed, before dried and ground to produce dehydrated palm oil mill effluent, or centrifuged in the wet state, after having undergone anaerobic, thermophilic and acidophilic fermentation. In the latter case, the product is known as fresh centrifuged sludge solids of 15 to 20% dry matter and may be dehydrated to form dry centrifuged sludge solids of between 94 and 97% dry matter (Table 4.3). The composition of the essential amino acids in palm oil sludge and palm kernel meal is given in Table 4.10. Although, there is insufficient information concerning the amino acid composition of different African oil palm products, data from Table 4.10 suggest that lysine is not present in an appropriate proportion in the protein.

Table 4.10. Composition of essential amino acids in palm oil sludge and palm kernel meal (% CP).

Amino acid Palm oil sludge Palm kernel meal Amino acid Palm oil sludge Palm kernel meal
Arginine 0.19 2.20 Methionine+cystine 0.28 1.98
Histidine 0.14 0.27 Phenylalanine+ tyrosine 0.77 1.28
Isoleucine 0.35 0.63 Threonine 0.34 0.54
Leucine 0.60 1.05 Tryptophan 0.12 0.17
Lysine 0.21 0.56 Valine 0.36 0.9

Source: Devendra (1977)

Fresh centrifuged sludge solids have been incorporated in a concentrate ration daily at a level of 14% total dry matter for pigs from 30 to 90 kilogrammes. The average daily gain and dry matter feed conversion for the maize control group and one of the experimental treatments containing fresh centrifuged sludge solids was: 700g, 3.36 and 650g and 3.83, respectively (Ong, 1982).

Dehydrated palm oil mill effluent has been incorporated up to 20% in dry rations for growing/finishing pigs; however, with increasing inclusion of dehydrated palm oil mill effluent, performance was poorer and carcass fat deposition increased (Table 4.11).

Table 4.11. The use of dehydrated palm oil mill effluent for growing/finishing pigs (19-92 kg).

0% 5% 10% 15% 20%
Maize, ground 78.9 74.9 70.4 65.9 61.4
Soya bean meal 13.5 12.5 12.0 11.5 11.0
Dehydrated palm oil mill effluent - 5.0 10.0 15.0 20.0
ADG, g 730 700 690 720 650
AD feed intake, kg/d 2.24 2.30 2.34 2.38 2.34
AD feed conversion 3.04 3.31 3.38 3.34 3.60
Fat, % of carcass 16.7 17.9 20.4 19.9 19.5

Source:Ong (1982); all diets contained. 5.5% fishmeal, 1.95% minerals and vitamins and 0.15% methionine

There have been numerous attempts to convert palm oil mill effluent into a viable animal feed resource; however, most methods have been discontinued due to the large initial capital investment required, and particularly to the cost of fuel for dehydration. In Malaysia, one method used to convert fresh palm oil mill effluent into a potential feedstuff involved concentration by centrifugation or decantation, followed by absorption on other dry feeds like tapioca chips, grass meal or palm kernel meal. The absorption process can be repeated several times before final dehydration (Webb, Hutagalung and Cheam, 1976, cited by Devendra et al., 1981).

Perhaps, one idea would be to promote the use of the fresh centrifuged sludge solids (15-20% dry matter) for finishing pigs which, compared to younger animals, have a greater capacity to effectively use larger amounts of more liquid feeds. To date, apparently, this material has only been used in dry, concentrate rations (Ong, 1982). This approach might require supplementation to increase the crude protein content to that of a cereal, as well as some molasses to improve palatability. It would have to be fed immediately, preferably near the factory in order to avoid transportation of a product that contains 80% of water. Interestingly, this approach was indicated by Devendra et al. (1981) for feeding sheep and cattle (Devendra, 1992); he referred to the use of this residual product alone, or combined with oil-rich fibrous residue. Perhaps, this same recommendation might be applied to feeding pigs.

In Ghana, oil palm slurry (sludge) has been used to replace 15, 20, 25 and 30% of maize in ad libitum diets for growing pigs to 70 kg. The control group was fed a maize-based diet; performance was not affected by the use of sludge. It was emphasized that with the exception of the loin-eye area, carcass measurements were improved when pigs were offered the slurry-containing feed (Abu et al., 1984). The use of unconventional feeds for pigs in Ghana was also studied by Hertrampf (1988), who reported using oil palm sludge in place of maize at a level of from 15 to 30 percent. An increase in the daily feed intake and the average daily gain, in addition to a significant reduction in feed costs, was reported.

Palm kernel meal

The palm kernel represents 5% of the weight of the fresh fruit bunch; it contains approximately 50% oil (Beltrán, 1986). The meal is produced by extracting the oil from the kernel within the palm nut. The resultant meal, sometimes also referred to as "palm kernel cake", can contain from 12 to 23% of crude protein depending upon the efficiency of the process used to extract the oil (Table 4.12) .

As expressed earlier, the first oil palm by-product reportedly used for feeding pigs was the extracted and non-extracted palm kernel meal. It was first used in Europe as a substitute for wheat bran in rations for growing/finishing pigs. Currently, because of its poor palatability and high fibre content, it is more commonly fed to ruminants where it produces a hard, white carcass fat in meat animals and a saturated fatty acid profile in the milk of lactating animals (PNI, 1990).

In Nigeria, palm kernel meal was used for pigs but it ranked lowest in protein quality compared to other local protein sources and produced a loss in weight (Fetuga et al., 1974, cited by Devendra, 1977). However, in Colombia, good results have been reported (Ocampo, 1994b) when almost 40% of palm kernel meal was used in the form of a restricted protein supplement that also contained soya bean meal. Correct storage, to reduce the risk of mould and the production of aflatoxins, was emphasized. The chemical composition and digestibility of palm kernel meal is shown in Table 4.12.

Table 4.12. Chemical composition/digestibility of palm kernel meal for pigs (%).

average composition digestibility
Dry matter 90 -
Crude protein 16 60
Crude fibre 16 36
Nitrogen free extract 48 77
Ether extract 10 25

Source: PNI (1990)

Whole fresh palm fruit

The chemical composition of the flesh (mesocarp) which surrounds the palm nut, and interior kernel, is presented in Table 4.13. The whole fresh palm fruit constitutes a potential energy feed resource for the small-scale pig producer without access to factory produced palm oil derivatives, such as, crude oil or oil-rich fibrous residue. In an experiment to determine the performance of pigs from 27 to 90 kg, fed twice daily with a restricted amount of protein, and whole fresh palm fruit as a partial or complete replacement for sorghum, Ocampo (1994a) surprisingly found that, apart from consuming easily the fibrous material adjuring to the nut, the pigs often ate the entire fruit including the palm nut and the interior kernel. It was observed that first they ate the fibrous material surrounding various nuts, accumulated the nuts, then proceeded to crack and extract the kernel within the nuts. One interesting observation was that when the fresh fruit was stored for more than seven days, palatability, and therefore voluntary consumption, was noticeably affected.

Table 4.13. The chemical composition of the pulp (mesocarp) and kernel of the fruit of the African oil palm (% DM).

pulp kernel
Crude protein 9.26 11.9
Crude fibre 25.5 31.6
Nitrogen free extract 31.3 25.9
Ether extract 28.6 26.9
Ash 5.4 2.5

Source: Ocampo (1994b)

Although the data in Table 4.14 show that best growth was obtained when only 25% of the fresh fruit was used in place of sorghum, it was emphasized that best economic gains were when 75 or 100% of the fruit was used. In a second trial, Ocampo (1994c) used 4 groups to study the optimum amount of rice polishings as a source of carbohydrate for growing/finishing pigs, also fed a restricted protein supplement (500 g/day) and whole, unprocessed African oil palm fruit, fed ad libitum. The amount of rice polishings offered during the growing phase (20-60 kg) was 100, 200, 300 and 400 g/day, and during the finishing phase (60-90 kg), 150, 250, 350 and 450 g/day. During the entire experimental period, the average consumption of the fresh fruit was 1.1, 1.1, 1.0 and 0.9 kg AD/day; the average liveweights were: 485, 515, 492 and 497 g/day and dry matter conversions were: 3.20, 3.20, 3.30 and 3.30, respectively. Reportedly, the most economic levels of rice polishings were 200 g/day during the growing phase and 250 g/day during the finishing phase.

Table 4.14. Whole fresh palm fruit (WFPF) as a partial or complete replacement for sorghum in diets for pigs from 27-90 kg.

% WFPF 25% 50% 75% 100%
Initial liveweight, kg 28.1 27.0 26.7 27.0
Final liveweight, kg 89.3 85.7 90.2 85.7
Days to finish 98 98 126 126
AD feed * intake, kg/d: sorghum

        oil palm fruit

1.30

0.54

0.86

0.97

0.20

1.43

0.00

1.53

ADG, g 625 598 503 466
DM feed intake, kg/d 2.02 1.94 1.68 1.59
DM feed conversion 3.20 3.20 3.30 3.40

Source: Ocampo (1994a); *also fed 500 g/d of protein supplement : soya bean meal, 97.6%; dicalcium phosphate, 2%; salt, 0.3% and vitamin/mineral premix, 0.3 percent

For the low income farmer in the tropics, the possibility to fatten a pig with one's own fresh palm fruit, and perhaps purchase only 60 kg of a high-quality protein supplement, or even use some rice polishings, is definitely an example of an alternative feeding system for pigs. This same author also emphasized that if a feeding system based on the whole fruit was used, there would be approximately 100 g/day of protein availabe to the pig via the kernel, and that this fact merited even further study. Obviously, the African oil palm has definite potential as a feed resource for pigs in the tropics. Perhaps, its utilization might be improved if more basic information related to its nutritional value was available.

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