Feeding value of copra meal

CM is obtained from the coconut fruit which has been sun-dried or mechanically dried. CM is generally produced by the extraction of oil from the coconut kernel using expeller machines or solvent extraction (Table 1).

Table 1

Nutrient content and physical characteristics of copra meal.

*NDF: Neutral detergent fibre; (1) Sundu et al., Reference SUNDU, KUMAR and DINGLE2004b; (2) Thorne et al., Reference THORNE, WISEMAN, COLE and MACHIN1989; (3) NRC, Reference NRC1994; (4) Panigrahi et al., Reference PANIGRAHI, MACHIN, PARR and BAINTON1987.

The quality of CM available commercially varies from one batch to another. There are three main factors, apart from its intrinsic nutrient content and its physical properties that influence CM quality as a poultry feedstuff. These include the extraction process, storage conditions and the drying process. Studies on the effects of different extraction processes on the quality of CM have been undertaken by a number of workers (Thorne et al., Reference THORNE, WISEMAN, COLE and MACHIN1989: Thomas and Scott, Reference THOMAS and SCOTT1962). Solvent extracted CM is better quality in terms of protein content and quality (Thomas and Scott, Reference THOMAS and SCOTT1962) than expeller CM. Heating is generated in an expeller machine and this can lead to thermal damage of the protein. Humid storage conditions impair the quality of CM due to the possibility of aflatoxin growth on the product. Sutikno (Reference SUTIKNO1990) found that 58% of CM tested was contaminated by aflatoxin, particularly aflatoxin B1 (Pue et al., Reference PUE, KALUWIN, SUNDARRAO, SINGH and BURROWS1991). These two findings were reported from Indonesia and Papua New Guinea, which are high humidity countries. The amount of aflatoxin in CM exponentially increased when it was stored for more than five weeks (Head et al., Reference HEAD, SWETMAN and NAGLER1999). Drying is also found to be a factor affecting CM quality as a result of heat damage of protein (Guarte et al., Reference GUARTE, MUHLBAEUR and KELLERT1996).

Copra meal protein

Copra meal protein content varies depending on the coconut origin and the type of oil extraction process. Solvent-extracted coconut protein content tends to be higher, (24.6%; Thorne et al., Reference THORNE, WISEMAN, COLE and MACHIN1989) and 25.5%; Rama et al., Reference RAMA, DORAISWAMY, INDIRA and MAHADEVIAH1965) than the protein content of expeller pressed coconut meal, (15.4–21.8%; Thorne et al., Reference THORNE, WISEMAN, COLE and MACHIN1989). With a total world production of CM of 2 million tonnes/year (FAO, Reference FAO2002), this is equivalent to more than 480,000 tonnes of crude protein which is available for animal feeding from CM.

Copra meal is generally low in lysine and sulphur amino acids (see Table 2). CM only meets 45–50% and 34–62% of the lysine and methionine requirements respectively for young chicks (NRC, Reference NRC1994 and Lachance and Molina, Reference LACHANCE and MOLINA1974). The low content of lysine, coupled with the susceptibility of lysine and other amino acids to binding in the Maillard reaction during heating either in the drying or oil extraction process, indicates that amino acid quality can be low. Other amino acids such as tryptophan and threonine are not sufficient to meet chicken needs (NRC, Reference NRC1994). Therefore the utilisation of CM as a source of protein can lead to a deficiency of amino acids, especially if it is used as a high proportion of a diet. Arginine content, on the other hand, is relatively high and thus increases the arginine to lysine ratio. Since arginine and lysine have an antagonistic effect (D'Mello and Lewis, Reference D'MELLO and LEWIS1970), an appropriate ratio should be ensured when the diet is fed to chickens. However, Balnave et al. (Reference BALNAVE, HAYAT and BRAKE.1999) stated that the high arginine to lysine ratio in CM can improve the resistance of animals to heat stress.

Table 2

Amino acid content of two copra meals (A and B) (gkg^-1).

A: NRC (Reference NRC1994); B: Lachance and Molina (Reference LACHANCE and MOLINA1974)

NC : Not calculated, *Essential amino acids

The solubility of coconut protein has been found to be low. An enzymatic study of coconut protein was done by Lachance and Molina (Reference LACHANCE and MOLINA1974), who compared various enzymes used for extraction of protein. Their findings indicated that the inclusion of bromelain gave a higher solubility (0.35), followed by fungal prolase (0.28) and papain (0.26). In addition to these results, Krishnamoorty et al. (1995) stated that protein solubility of CM using protease enzyme was about 0.45. These findings indicated that different enzymes have different protein extractabilities. The digestibility of CM protein is variable depending upon the animal species used and the coconut extraction process. An in-situ study by Chandrasekariah et al. (Reference CHANDRASEKARIAH, SAMPATH, THULASI and ANANDAN2001) indicated that protein degradability of CM in the rumen was only 0.33. Studies in other monogastrics (pigs) showed that coconut protein digestibility was about 0.51 (Creswell and Brooks, Reference CRESWELL and BROOKS1971). No data is available on the digestibility of CM protein in broiler chickens. Unpublished data indicates that the faecal digestibility and ileal digestibility of CM protein for broiler chickens are 0.55 and 0.63 respectively.

Copra non starch polysaccharides (NSPs)

Three of the earliest and still the most commonly used methods for identification of complex carbohydrates or fibre are the crude fibre method and two detergent methods. Over the last two decades, modified methods have been developed to analyse non-starch polysaccharides (see Knudsen, Reference KNUDSEN2001). More than 60% of the nutrient components of copra have been analysed as neutral detergent fibre (NDF) which is mainly cellulose and hemicellulose (see Table 1). This indicates that the major component of coconut carbohydrate is in the form of dietary fibre. Coconut NSPs have been isolated, characterized and quantified by a number of workers. An early study by Balasubramaniam (Reference BALASUBRAMANIAM1976) indicated that NSPs in coconut are mostly in the form of mannan (26%), galactomannan (61%) and cellulose (13%). Studies on the digestibility of coconut mannan in poultry diets are not available. Galactomannan, another major polysaccharide in coconut meal, is made up of a chain of β (1-4) –D-manopyranose units to which the galactose residue attaches as a side chain of D-galactopyranose units (Aspinal, Reference ASPINAL1970). Rao and Bagchi (Reference RAO and BAGCHI1961) found mannan and galactomannan but not glucomannan in CM. A more recent study by Saittagaroon et al. (Reference SAITTAGAROON, KAWAKISHI and NAMIKI1983) demonstrated that mannan is the major polysaccharide in coconut meal and represents 61% of total polysaccharides., and the residue of alkali extraction found by the author contained mannose (42%) and glucose (58%). The presence of mannose and glucose found can be interpreted as glucomannan or a mixture of mannan and cellulose. From these two studies it may be hypothesized that copra NSPs are mainly cellulose and mannan as their presence was identified by a previous study of Balasubramaniam (Reference BALASUBRAMANIAM1976) and neither Rao and Bagchi (Reference RAO and BAGCHI1961) nor Balasubramaniam, (Reference BALASUBRAMANIAM1976) found the presence of glucomannan in the coconut meal. Supporting the finding of Saittagaroon et al. (Reference SAITTAGAROON, KAWAKISHI and NAMIKI1983), Dusterhoft et al. (Reference DUSTERHOFT, VORAGEN and ENGELS1991) stated that mannan is the predominant NSP in coconut meal.

A comprehensive study on the comparison of NSPs in several feedstuffs has been carried out by Knudsen (Reference KNUDSEN1997). The researcher found that copra meal contained 42.2% NSP, mostly as water insoluble non-cellulosic polysaccharides. Coconut monosaccharides are water soluble (such as galactomannan; Aspinal, Reference ASPINAL1970) and water insoluble (such as mannan; Aspinal, Reference ASPINAL1970). Non-cellulosic polysaccharides contain arabinose, xylose, mannose, galactose and glucose (Knudsen, Reference KNUDSEN1997), although this research did not identify or quantify the kind of NSP. After examining the monosaccharide residues in CM, several NSPs can be expected to be present, including arabinogalactan and galactomannan. This prediction seems to be relevant to the findings of Saittagaroon et al. (Reference SAITTAGAROON, KAWAKISHI and NAMIKI1983), who identified small amounts of arabinoxygalactan, galactomannan, arabinomannogalactan and galactoglucomannan, all of which contain some of the monosaccharides identified by Knudsen (Reference KNUDSEN1997).

Physical properties of copra meal

Physical properties of the feed can be used as predictors to determine the feeding value of the ingredients and diets (Mratz et al., Reference MRATZ, BOUCHER and MC CARTNEY1957 and Kyriazakis and Emmans, Reference KYRIAZAKIS and EMMANS1995). Two important physical characteristics that should be considered in poultry diet formulation are bulk density and water holding capacity (WHC). These two physical characteristics may be associated with the chemistry of the constituent of polysaccharides and lignin (Eastwood, Reference EASTWOOD1973) and play important roles in decreasing feed intake (see Kyriazakis and Emmans, Reference KYRIAZAKIS and EMMANS1995) which is subsequently impairs the productivity of birds.

The low bulk density (see Table 3) and high WHC of CM contribute to a decreased feed intake of birds due to its high bulking properties (see Sundu et al., Reference SUNDU, KUMAR and DINGLE2005b). The mechanism of these two physical characteristics affecting feed intake is that a low bulk density diet occupies more space in the digestive tract. This becomes critical when bulky ingredients have a high WHC. The ability of CM to bind water led to the birds consuming more water than the birds fed a lower WHC diet (Sundu et al., Reference SUNDU, KUMAR and DINGLE2005a). This led to less feed and nutrients being consumed. It is clear that the low feeding value of CM is not only contributed by its high dietary fibre and imbalanced nutrients, but also by its physical properties.

Table 3

Physical characteristics of copra meal compared with other feedstuffs.

Amino acid and enzyme supplementation

Despite the fact that CM is rich in protein (up to 25%), and can thus meet the crude protein demands for young chicks and adult broilers, its quality was reported to be low due to two major reasons: (1) heat treatment (during either the drying or oil extraction processes) depresses the nutritive value because of the sensitivity of protein to heat damage (Butterworth and Fox, Reference BUTTERWORTH and FOX1963), (2) the high fibre content of the CM (cellulose and hemicellulose) interferes with the digestibility of nutrients (Rama et al., Reference RAMA, DORAISWAMY, INDIRA and MAHADEVIAH1965) as protein is located inside the cell which is surrounded by the fibrous cell wall. Accordingly, the inclusion of CM in the diet without any nutrient adjustment should be limited as it could impair the performance of the birds. To cope with these two problems, both the addition of essential amino acids, to supplement the low content and to replace the heat damaged amino acids, and enzyme application, particularly mannan degrading enzymes to break down the cell wall, are possible adjustments.

Early recommendations for using CM in broiler diet were limited to 20% inclusion rates. However, it was found that for young chicks (21 days), the inclusion of CM in the diet at only 10% gave a negative effect on the productivity of the birds kept for 2–3 weeks (Sundu et al., Reference SUNDU, KUMAR and DINGLE2004a, Reference SUNDU, KUMAR and DINGLE2004b). Efforts to increase the inclusion of CM in the diet have been made by Thomas and Scott (Reference THOMAS and SCOTT1962) through supplementation with lysine. The authors formulated a 40% CM diet with three different energy contents. They found that the addition of lysine increased body weight of broilers. However when it was compared with a corn-soy diet, the growth of broilers was still low. More recent findings indicated that the use of up to 25% was still safe provided that two essential amino acids, lysine and methionine, were included and the birds were maintained to 6 weeks of age (Panigrahi et al., Reference PANIGRAHI, MACHIN, PARR and BAINTON1987).

Sundu et al. (Reference SUNDU, KUMAR and DINGLE2005b) increased the inclusion of CM to 30% when supplemented with lysine and methionine in a diet balanced for metabolisable energy and digestible amino acids. When the birds were kept up to 6 weeks, the final body weight of birds was far below the body weight of birds fed the control corn-soy diet. This may justify the conclusion that a diet balanced for amino acids and metabolisable energy can only be tolerated at the level of 25% CM by broilers.

The inability to improve the feeding value of CM by amino acid supplementation in young chicks may be due to the smaller capacity of the digestive systems of young chicks (Sundu et al., Reference SUNDU, KUMAR and DINGLE2004b) and poor capability to release and digest nutrients inside the cell wall such as protein. These two problems led to a decreased weight of food consumed and therefore decreased nutrient intake. It is not difficult to conclude that when the birds consume small amounts of feed containing major components of indigestible nutrients, the bird's productivity is impaired.

Supplementation with exogenous enzymes could help to break down the dietary fibre. The efficacy of using enzymes has been proven in numerous publications, especially with respect to the use of glucanases in barley and xylanases in wheat (Ravindran et al., Reference RAVINDRAN, SELLE and BRYDEN1998). Since β-mannan is the major component of copra carbohydrates, supplementation with mannan degrading enzymes could be beneficial. In the laboratory, the use of mannan degrading enzymes hydrolysed crude fibre (possibly containing mannan and cellulose), by up to 50% (Teves et al., Reference TEVES, ZAMORA, CALAPARDO and LUIS1989). A detailed laboratory study by Kusakabe and Takashi (Reference KUSAKABE and TAKASHI1988) indicated that copra mannan was hydrolysed into a small amount of mannose (3.3%), a large amount of mannobiose, mannotriose and mannotetraose (75.3%) and some manno-oligosaccharides (21.4%). Few studies have been documented regarding the use of enzymes to improve the quality of CM. One of the first studies on the use of enzymes in a CM-based diet was reported by Pluske et al. (Reference PLUSKE, MOUGHAN, THOMAS, KUMAR and DINGLE1997), who found that the use of a mannan degrading enzyme improved body weight and decreased mortality of broiler chickens (Table 4). Manganese enzyme increased the dry matter digestibility and AME of the diet (Sundu et al., Reference SUNDU, KUMAR and DINGLE2004b). Protein, lipid and crude fibre digestibilities were improved when the CM was initially hydrolysed overnight with enzyme solution before CM was included in the diet (Teves et al., Reference TEVES, ZAMORA, CALAPARDO and LUIS1989).

To maximise the feeding value of CM, the use of multi-enzyme mixtures may increase the digestibility of the nutrients. This is due to the fact that mannan and galactomannan only represented about 36% of total dry matter (Balasubramaniam, Reference BALASUBRAMANIAM1976; Knudsen, Reference KNUDSEN1997) and the remaining dry matter consists of other NSPs, protein, lipid, starch and vitamins and minerals, which are essential for maintenance, growth and production. Sundu et al. (Reference SUNDU, KUMAR and DINGLE2005a) combined two enzyme products, a mannan degrading enzyme and a multi enzyme mixture (Allzyme SSF^®), and found that body weight of birds were improved significantly so that they were not significantly different from those of birds fed a control corn-soy diet.

Table 4

Performance of chicken broilers fed a copra meal based diet treated in various ways.

* Thomas and Scott (Reference THOMAS and SCOTT1962); ** Pluske et al. (Reference PLUSKE, MOUGHAN, THOMAS, KUMAR and DINGLE1997); *** Sundu et al. (Reference SUNDU, KUMAR and DINGLE2005b)

The pattern of growth of birds fed a 25% CM diet compared with a control (corn-soy) diet was reported by Panigrahi et al. (Reference PANIGRAHI, MACHIN, PARR and BAINTON1987). Body weight and feed intake of birds fed the CM diet were significantly lower before the birds reached six weeks of age but after then they were not different. This reveals the considerable adaptive capacity of birds by increasing feed intake to the level of those fed a corn-soy diet. When Sundu et al. (Reference SUNDU, KUMAR and DINGLE2005a) increased the inclusion rate of CM to 30% in the diet, the body weight of birds was lower than controls at six weeks of age, even though there was a tendency for the birds to accelerate their growth during weeks five and six. However when the 30% CM diet was supplemented with a combination of enzymes, the authors found the same pattern as the earlier finding of Panigrahi et al. (Reference PANIGRAHI, MACHIN, PARR and BAINTON1987) in which birds fed the supplemented diet could increase their growth rate after five weeks of age. This indicates that enzymes work well in older birds. This hypothesis is based on the fact that the passage time of digesta in older birds was longer than in young chicks (Duke, Reference DUKE1986). In the older bird, the enzyme has a longer reaction time in the digestive tract of bird, and this will, in turn, improve feed digestibility and the performance of birds.

Physical treatment of copra meal based diets

Pelleting and crumbling

Low bulk density ingredients like CM will occupy more space in the digestive tract of bird and this can affect the capacity of digestive organs to hold digesta. Accordingly, the birds fed the low bulk density diet consequently consumed less food as found in all studies on the use of a CM diet (Thomas and Scott, Reference THOMAS and SCOTT1962; Panigrahi, Reference PANIGRAHI1992; Sundu et al., Reference SUNDU, KUMAR and DINGLE2004a). Sundu et al. (Reference SUNDU, KUMAR and DINGLE2005a) pelleted and crumbled CM and then added it to broiler diets, whereby the bulk density increased by 25%. This would benefit handling, transport cost and less space occupied for storage.

The use of pelleted diets has been practised for more than 65 years since the report of Patten et al. (Reference PATTEN, BUSKIRK and RAULS1937) was published. The positive effect of using pelleted diets both in management and feeding value has been well documented (Callet, 1965; Thomas and Van der Poel, Reference THOMAS and VAN DER POEL1996; McCracken, 2002). There is no doubt that the body weight and feed intake of broilers fed a pelleted diet are improved (Mitchell et al., Reference MITCHELL, WALDROUP, HILLARD and HAZEN1972). Improvements in the body weight of birds fed a pelleted diet are thought to be realised through three main mechanisms;

1. (1) the increase in feed intake

2. (2) the increase in feed digestibility

3. (3) less energy spent.

Increased feed intake of pelleted diets compared with a mash has been reported by a number of workers. Pelleting the whole diet has been found to be beneficial for the improvement of bird performance (Callet, 1965; Proudfoot and Hulan, Reference PROUDFOOT and HULAN1982; Nir et al., Reference NIR, HILLEL, PTICHI and SHEFET1995). Accordingly, pelleted diets are the main commercial product in the broiler industry today.

As the main problem of CM in the diet appears to be its low bulk density, pelleting CM alone, instead of the whole diet, may still give a positive effect on improving bird performance. To verify this hypothesis, Sundu et al. (Reference SUNDU, KUMAR and DINGLE2005a) initiated a study of adding pelleted CM to the diet. The authors found that pelleting CM increased the body weight of broilers to the extent that it overtook the body weight of the birds fed a corn-soy control diet due to increased feed intake but feed digestibility was not changed. This finding may justify the conclusion that the main contributing factor to an increased feeding value of pelleted or crumbled CM is its increased bulk density. Although CM may undergo chemical change during pelleting or crumbling, this effect seems not to benefit the birds as the feed digestibility remained unchanged (Sundu et al., Reference SUNDU, KUMAR and DINGLE2005a). Our unpublished data supports this hypothesis because when pelleted or crumbled CM was reground and fed to the birds, their growth was very slow.

This finding justifies the conclusion that pelleting is needed when the diet contains low bulk density ingredients. The growth response of broilers fed the pelleted/crumbled CM diet was optimal from day one. However, further studies are needed to verify this finding for other low bulk density ingredients. Just pelleting and crumbling the low bulk density ingredient also needs to be compared with pelleting and crumbling the whole diet.