Livestock Research for Rural Development 15 (7) 2003

Citation of this paper


The use of ensiled cassava leaves in diets for growing pigs.

1. The effect of graded levels of palm oil on N digestibility and N balance

Chhay Ty, T  R Preston and  J Ly*


University of Tropical Agriculture Foundation
Chamcar Daung, PO Box 2423, Phnom Penh 3, Cambodia

* Present address: Swine Research Institute,
PO Box 1, Punta Brava, La Habana, Cuba



Four Mong Cai x Large White castrate male pigs weighing on average 9.6 kg were alloted at random into four diets to study the effect of graded levels (0, 5, 10 and 15% in dry basis) of refined palm (Elaeis guineensis, Jacq.) oil introduced in diets of broken rice and ensiled cassava leaves to study nutrient digestibility and balance of N according to a 4x4 Latin square design. The silage was made from sun-dried, wilted, chopped leaves of cassava  harvested after 4.5 to 5 months of growth. The cassava leaves were ensiled with 5% of sugar palm (Borassus flabellifer) syrup and stored during 30 days in plastic containers of 100 kg capacity.

The characteristics of the silage were pH 4.10, DM 50.7 %, ash 14.1, organic matter 85.9, NDF 47.0, crude fibre 35.3, and N 3.92 % in dry basis, respectively. The cyanide content of the silage was 110 mg/kg DM. Mean environmental temperature was 35oC at midday (12:00) during the trial (May 2002). Observed feed intake was slightly lower than that programmed (50 g DM/kg body weight) and was on average 45.6 g DM/kg body weight. A non significant slight increase of feed intake from 88.4 to 92.2% from that programmed was found with increasing levels of dietary palm oil. During the entire trial the pigs were in a positive body weight balance and there were no symptoms of animal discomfort. Dry matter and organic matter digestibilities were decreased as the level of dietary refined palm oil was increased.  Energy digestibility was not significantly influenced by graded levels of palm oil in the diet.  In contrast, ether extract digestibility increased significantly (P<0.001) with increased levels of refined  palm oil in the diet. The digestible energy content of the diets increased from 14.03 to 17.26 MJ/kg DM with increasing levels of palm oil. Neither N digestibility nor N retention were affected by the inclusion of refined palm oil in the diet. N digestibility was relatively low (overal mean, 66.7%) but N retention as related to N digested was high (overall mean, 82.7%).

It is suggested that if refined palm oil is included in the diet up to 15% of the DM, there will be no adverse effect on nutrient digestibility and N balance of pigs fed diets based on high levels of ensiled cassava leaves and broken rice.  

Key words:  pigs, ensiled cassava leaves, digestibility, N retention, refined palm oil



The use of ensiled cassava leaves for pigs and other animal species has been studied in different opportunities (see for example, Bui Van Chinh and Le Viet Ly 2001). In this connection, it has been shown the potential of leaves from cassava as a protein source in pig nutrition in the tropics (Bui Van Chinh et al 1992; Bui Huy Nhu Phuc et al 1996; Du Thanh Hang 1998; Nguyen Thi Loc et al 2000). On the other hand, considerable efforts have been devoted to study the ensiling process and its relationship with cyanide elimination from the leaves (Bui Van Chinh 1990; Ravindran 1990; Limon 1992; Chhay Ty et al 2001).            

One of the characteristics of the ensiled cassava leaves is the relatively low energy density, due to the fact that the high cell wall content results in decrease in the total tract digestibility of energy. Therefore, the inclusion of a high energy density feedstuff in the diet, such as palm (Elaeis guineensis, Jacq) oil, could facilitate an improved animal performance in diets with a high proportion of cassava leaves, without any deleterious effect on energy utilization by the animals. In this connection, several factors influencing the nutritive value of ensiled cassava leaves have recently been examined (Du Than Hang et al 1997; Nguyen Van Lai and Rodríguez 1998; Du Than Hang 2000; Ly et al 2001). However, little if any is known about the nature of the interdependence of such a mixture of ensiled cassava leaves and palm oil and its effect on the nutritive value of the diet for pigs.

The aim of the present experiment was to study the effect of the inclusion of graded levels of palm oil in the diet on nutrient digestibility and energy balance of pigs fed a high level of ensiled cassava leaves.

Materials and Methods

Location and climate

The experiment was carried out in the ecological farm of the University of Tropical Agriculture Foundation (UTA), located in Chamcar Daung, in the outskirts of Phnom Penh City, Cambodia. The ambient temperature was about 350C in the middle of the day (12:00) during the trial in May 2002.

Experimental feeds

Cassava leaves were harvested after 4.5 to 5 months of growth from farmer’s fields in Kandal province, Cambodia. Stems and petioles were removed from the leaves and then the foliage product was sun-wilted for half a day before being chopped into small pieces and ensiled with 5% of sugar palm (Borassus flabellifer) syrup diluted with water 1:1 (fresh basis). Leaves and syrup were carefully mixed and  stored in plastic bags, inside rigid plastic containers. The bags were tightly closed to prevent air contact and stored for 30 days before feeding. Every container thus prepared contained approximately 100 kg of fresh material. The ensiled cassava leaves had a pH of 4.10 and DM content of 50.7%. Other characteristics of the ensiled product were: ammonia 37.6 mg/100 g DM, total acidity 83.6 meq/100 g, cyanide 111 mg/kg DM.

Four diets (Table 1), were formulated to contain 45% ensiled cassava leaves (DM basis), broken rice and fish meal, partially substituted by refined palm (Elaeis guineensis, Jacq) oil originally from Malaysia and currently available in the local market. Broken rice and fish meal were of Cambodian origin.


Table 1. Characteristics of the diets (percentage in dry basis)


Ensiled cassava leaves

Refined palm oil, %











Ensiled cassava leaves






Refined palm oil












Broken rice






Sugar palm syrup






Vitamins and minerals1






Analysis (%)






Dry matter












Organic matter












Crude fibre












Crude fat






Crude protein (Nx6.25)






GE, MJ/kgDM2






1 According to NRC (1998) recommendations

2 Calculated according to Nehring and Haenlein (1973. For further details, see text


Experimental design


The experiment was done according to a 4*4 Latin Square arrangement of 4 dietary treatments with four Mong Cai x Large White castrate male young pigs weighing on average 9.6 kg. The animals were housed in metabolism cages during the whole trial. The metabolism cages (80 x 80cm) were built to allow the quantitative collection of faeces and urine (Photo 1). The characteristics of the cages have been described elsewhere (Chiev Phiny and Rodriguez 2001). The metabolism cages were installed in an open stable. Each experimental period consisted of five preliminary days when the animals were adapted to the diets followed by another five days for collection of faeces, urine and feed refusal.

Photo 1: The metabolism cage used in the experiment


The pigs were fed thrice daily with equal rations at 8:00 am, 12:00 am and 3:00 pm. The cassava leaf silage was mixed with the other components of the ration. Feed intake was programmed to be 50 g DM/kg bodyweight, and water was permanently supplied through drinking nipples. The animals were weighed at the beginning of the trial and every ten days.


Data collection


Feed refusals and faeces were collected every day and were kept frozen in plastic bags until analysis. A representative sample was obtained from every type of thawed material after a careful homogenization. At the end of each period, feed refusals and faeces were mixed thoroughly by hand and then homogenized in a coffee grinder, prior to taking representative samples that were analysed for DM, N, Crude fibre, NDF, crude fat and ash. Urine was collected in a plastic bucket to which sulphuric acid was added to maintain the pH below 4.0. At the end of each period the volume was measured and a sample analysed for N.


Chemical analyses


Chemical analyses of the feed ingredients, diets and faeces were undertaken following the methods of Goering and Van Soest (1970) and Van Soest et al (1991) for NDF, and AOAC (1990) for ash, N, crude fibre and ether extract. The DM content was determined using the microwave method of Undersander et al (1993). Fresh faeces were analyzed for pH with a glass electrode. The N content of urine was determined by the AOAC (1990) procedures. All the analyses were conducted in duplicate. The gross energy of diets and faeces was calculated according to energy coefficient values of 5.72, 9.50, 4.79 and  4.05 kcal/per cent of crude protein, ether extract, crude fibre and NFE, respectively (Nehring and Haenlein 1973). Thereafter, total digestibility of energy was estimated by standard methods of calculation. The conversion coefficient of 4.184 kjoule/kcal was used in the appropriate circumstances.


Statistical analyses


The data were subjected to analysis of variance according to the general linear model of the Minitab software (Minitab release 12; 1998). In the required cases means were separated by the Duncan’s multiple range test procedure (Steel and Torrie 1980). The model used was:

Yijk = m + Ti + Pj +ak + eijk   where  


Y = Dependent variable

m = overall mean

Ti = treatment effect

Pj = period effect

Ak = animal effect

eijk = random error



The pigs gained weight during the trial and there were no symptoms of intoxication due to the consumption of ensiled cassava leaves. A slight decrease in voluntary feed intake, relative to the programmed amount, was observed in all treatments (Table 2). However, there was no treatment effect (P>0.05) on this index, which averaged 45.6 g DM/kg body weight.  

Table 2. Feed intake in young pigs fed ensiled cassava leaves and palm oil (the programmed amount was 50 g DM/kg body weight)


Refined palm oil, %









DM intake







g/pig per day







g/kg body weight







Observed, % programmed









There was no significant dietary effect on measured faecal characteristics (Table 3). The alkaline reaction of faeces was noteworthy. On the other hand, overall faecal DM was relatively high.  


Table 3. Faecal characteristics in young pigs fed ensiled cassava leaves and palm oil


Refined palm oil, %










Faecal pH







DM, %







Faecal excretion, g/kg DM intake

Fresh material

523 a

634 b

687 c

637 bc



Dry matter

226 a

260 b

273 bc

288 c




297 a

374 b

414 c

348 b



abc Means without letters in common differ significantly (P<0.05)


Overall, digestibility values for DM were low (Table 4). The refined palm oil used in the experiment decreased the digestibility indices of dry matter and organic matter (P<0.01). The digestibility of ether extract increased as the level of palm oil was increased (P<0.001). Digestibility of energy did not change by the introduction of graded levels of refined palm oil in the diet, and was on average 73.3%. As a consequence of higher gross energy values of the diet, the digestible energy content of the diet increased from 14.0 to 17.3 MJ/kg DM when the level of refined palm oil in the diet was increased from 0 to 15%.  


Table 4. Nutrient digestibility in young pigs fed ensiled cassava leaves and palm oil


Refined palm oil, %










Total tract digestibility, %

Dry matter

77.4 a

74.0 b

72.7 bc

71.2 c



Organic matter

81.2 a

78.1 b

76.7 bc

75.2 c










Crude fibre








98.7 a

97.4 a

97.7 a

93.7 b



Ether extract














Dietary energy, MJ/kg DM

Gross energy







Digestible energy







abcd Means without letters in common differ significantly (P<0.05)


Figure 1. Relationship between digestibility of ether extract and level of palm oil in pigs


On all diets the digestibility of N was rather low; in contrast, the retention of N as percent of intake and of digested N was high (Table 5). There was no effect of the level of palm oil on these parameters.


Table 5. N balance in young pigs fed ensiled cassava leaves and palm oil


Refined palm oil, %










N balance, g/day














Faecal  excretion







Urinary excretion







N Digestibility, %







N retention














% of N intake







% of digested N









Feed intake


The use of high proportions of ensiled cassava leaves in the diet of pigs could be expected to reduce the voluntary feed intake, mainly due to the bulkiness of this feed. There are no previous reports concerning the effects on voluntary feed intake and growth traits in pigs when high levels of ensiled cassava leaves are included in the diet. In the present study, very few feed refusals were observed (see Table 2), which implies that the bulkiness of the diet was not limiting the feed intake.


The cyanide content of the cassava leaves could be another factor that could negatively influence voluntary feed intake of pigs, probably due to the bitter taste of the leaves (Ravindran et al 1987). Even so, González et al (1999) did not find any constraint to feed intake when 30% of cassava foliage from a bitter variety was included in the diet. The  bitter taste of cassava leaves could be highly masked by the strongly acidic nature of the silage, which had an average pH value of 4.10. A long term effect of cyanide on the pig’s voluntary feed intake has not been studied in detail (see for example, Tewe 1992). According to the analyses made on the silage, the cyanide level in the diets was some 50 mg/kg DM. This is below the recommended threshold of safety of cyanide concentration in food for human consumption (Gómez 1991). On the other hand, it was observed during the adaptation period of the animals to the metabolism cage and environment that the addition of sugar palm syrup at the moment of feeding the silage appeared to greatly enhance the voluntary feed intake of the mixed diet.


Fibre fractions and nutrient digestibility

Results from this experiment related to nutrient digestibility are in accordance with other previous studies where ensiled cassava leaves from a periodically cut plantation accounted for 50% of the diet (Ly and Pok Samkol 2001). Ly and Pok Samkol (2001) reported a DM digestibility value of 79.6%, which compares well with the data from this study using pigs fed a diet containing 45% ensiled cassava leaves of similar characteristics and no palm oil (77.4%, see table 4). Other data resulting from trials conducted with pigs fed ensiled cassava leaves of a probable high maturity are somewhat lower than those from these results (Bui Hong Ngu Phuc et al 1996; Du Than Hang 2000). It is known that with maturity, the fibrous fraction of cassava leaves changes its structure and proportions (Ravindran and Ravindran 1988), and this could increase the resistance to degradation in the digestive tract of the pigs.


On the other hand, Bui Hong Ngu Phuc et al (1996) and Du Thanh Hang (2000) showed that digestibility indices decreased with increasing level of inclusion of ensiled cassava leaves in the diet. However, little if any, is known on the influence of the degree of maturity of the cassava leaves maturity, and in consequence, the effect of possible changes in the linkage of nutrients to the fibre fractions, on nutrient digestibility in pigs. Several authors (King and Taverner 1975; De Goey and Ewan 1975; Kennelly et al 1978; Kennelly and Aherne 1980; Perez 1991) have found that a high content of fibre causes a reduction in the digestible energy concentration in pig rations. In this connection, Den Hartog et al (1988) found that apparent digestibility of organic matter and N were negatively  related to the dietary NDF. Similarly, Sandoval et al (1987) observed that there was a linear decrease in the digestibility of dry matter, crude protein, crude fibre, nitrogen free extract, organic matter and acid detergent fibre with increasing levels of dietary wood pulp. The total tract digestibility of nitrogen in pigs may fall by 1 to 1.5% in response to each 1% increase of dietary crude fibre according to INRA (1984). Other authors (Pond et al 1962; Cole et al 1967; Kass et al 1980; Just et al 1983; Frank et al 1983Noblet and Perez 1993) have observed that digestibility of nitrogen decreases with increasing dietary level of fibre. Sauer et al (1980) and Partridge et al (1982) also recognised that apparent crude protein and amino acid digestibility could decrease when additional fibre is included in pig diets.


Several factors have been mentioned to explain the mode of action of the different fibre fractions on total tract digestibility. Schneeman (1978) stated that fibre may absorb trypsin and chymotrypsin, as shown by a decrease in the activities of these enzymes. On the other hand, Just (1983) suggested that high levels of fibrous material in the ration could shorten the time for digesta to be enzymatically digested in the small intenstine, where the absorption of almost all nutrients takes place. Whittemore (1998) considered that non-starch polysaccharides reduce the digestibility of amino acid through coating and protecting effects. Some dietary protein is shifted away from the small intestine to the large intestine, where adsorption of amino acids is less efficient (Whittemore 1998).


It has been argued that, in contrast with a negative effect of fibre fractions on total tract digestibility of N, ileal digestibility of N is only very slightly affected in pigs fed different types and levels of fibre (Sauer et al 1991). Therefore, a negative effect of fibre on N disappearance in the large intestine, decreasing the extent of this process in this organ, could be even benefical for pigs, since this N is generally absorbed in non-amino acid forms by the pigs (Zebrowska 1973, Just et al 1981). This fact in turn should positively affect the energy metabolism of the animals, since an increase in the Krebs-Henseleit cycle in the liver to eliminate those N-compounds requires a considerable input of ATP. More information is necessary to support this theoretical discussion relating to possible factors influencing digestibility of nitrogenous compounds in pigs fed high levels of ensiled cassava leaves. Nevertheless, as a working hypothesis, it is proposed that a decrease in total tract digestibility of N in pigs fed high levels of cassava leaf silage does not necessarily result in a concomitant decrease in amino acid availability.


Dietary fat and nutrient digestibility

The results from the present experiment are in agreement with those from González et al (1999) who studied  graded levels of palm oil up to 10% in diets containing 30% cassava foliage. According to these researchers, digestibility of DM, NDF, N and organic matter was not affected by the level of dietary palm oil. In the Venezuelan report, an improvement in total tract digestibility of ether extract was observed when pigs were fed diets containing 30% of cassava foliage meal with increasing levels of refined palm oil, which also agrees with our results. Balogun and Fetuga (1984) also observed there was no negative effect of palm oil up to 10% of the diet on the N balance of piglets fed on cassava root diets. These observations are in accordance with those from this study. Le Duc Ngoan (1994) reported very low digestibility indices when Colombian palm oil was used in diets of fattening pigs based on sugar cane juice.  It is probable that the small number of observations (n=3) and the use of an indirect method for determining the total tract digestibility could have been factors leading to these low values. In contrast, Morgan et al (1984) found a total tract digestibility of palm oil as high as 95.8% in pigs. Eeckhout et al (1983) found that the digestibility of the ether extract of refined and crude palm oil was 86.0 and 85.4%, respectively.


There are a number of factors that can influence the nutritive value of diets containing different types and levels of lipids (Li et al 1990; Pech Sovanno et al 2002). Pettigrew and Moser (1991) and Leibbrandt et al (1995) observed that young pigs are less capable of digesting and utilizing dietary fat than are older pigs. Kurival and Bowland (1962) found that the digestibility of energy did not depend on the level of dietary fat; while Whittemore (1993) suggested that fat products with high levels of free fatty acids are less well digested.



 It is concluded that:

·    Up to 15% of palm oil can be included in the diet of pigs fed high levels of ensiled cassava leaves without affecting nutrient digestibility and N balance.

·    Adding palm oil to diets formulated with high levels of ensiled cassava leaves results in an increase in the digestible energy density in such diets.



The present experiment is part of a study on the use of ensiled cassava leaves and palm oil in pigs, supported by the MEKARN project financed by the SIDA-SAREC Agency. The authors express their gratitude to all the personal of the Ecological Farm, of the University of Tropical Agriculture Foundation, for help with the experiment, especially Mr. Keo Saeth for his assistance in taking care of the animals. Thanks are also expressed to Mr. Pok Samkol for analytical assistance in the laboratory of the Ecological Farm.  This paper formed part of the MSc thesis (MEKARN-SLU, Uppsala, May 2003), of the senior author.



AOAC 1990 Official Methods of Analysis. Association of Official Analytical Chemists. 15th edition (K Helrick editor). Arlington pp 1230

Balogun O O and Fetuga B L 1984 Influence of methionine an alm oil supplementation of cassava flour and soybean meal diets on performance, nitrogen retention and rate of tissue deposition in weanling pigs. Livestock Production Science 11:315-327

Bui Van Chinh, Le Viet Ly, Nguyen Huu Tao, Do Viet Minh 1992. "C" molasses and ensiled cassava leaves for feeding pigs. Results of research 1985-1990. Agricultural Publishing House, Hanoi. pp: 46


Bui Huy Nhu Phuc, Preston T R, Ogle B and Lindberg J E 1996 The nutritive value of sun dried and ensiled cassava leaves for growing pig. Livestock Research for Rural Development 8(3)


Bui Van Chinh 1990 The study of ensiling of cassava leaves and top. In: Development of Animal production in mountainous areas on North Vietnam. Hanoi pp 4-7


Bui Van Chinh and Le Viet Ly 2001 Studies on the processing and use of cassava tops as animal feed. Proceedings of the International Workshop “Current research and development on use of cassava as animal feed”. Khon Kaen University, Khon Kaen p 94

Chiev Phiny and Rodriguez L 2001 Digestibility and nitrogen retention in Mong Cai pigs fed sugar palm (Borassus flabellifer) juice and fresh water fish ensiled with rice bran and sugar palm syrup.. Livestock Research for Rural Development 13(2):

Chhay  Ty, Ly  J and Rodriguez  L  2001 An approach to ensiling conditions for preservation of cassava foliage in Cambodia. Livestock Research for Rural Development 13(3):

Cole, D J A, Duckworth J E and Holmes W 1967 Factors affecting voluntary feed intake in pigs. Animal Production. 9:141-148

DeGoey L W and Ewan R C 1975. Effect of levels of intake and diet dilution on energy metabolism in the young pig. Journal of  Animal Science. 40:1045-1051


Den Hartog, L A Huisman J, Thielen W J G, Van Schayk G H A, Boer H and Van Weerden E J 1988 The effect of including various structural polysaccharides in pig diets on ileal and faecal digestibility of amino acid and minerals. Livestock Production Science 18:157-170


Du Thanh Hang 1998 Ensiled cassava leaves and duckweed as protein sources for fattening pigs on farms in Central Vietnam. Livestock  Research for Rural development 10(3)


Du Thanh Hang, Nguyen Van Lai, Rodríguez L and Ly J 1997 Nitrogen digestion and metabolism in Mong Cai pigs fed sugar cane juice and different foliages as sources of protein. Livestock Research for Rural Development 9(2):

Du Thanh Hang 2000 Digestibility and nitrogen retention in fattening pigs fed different levels of ensiled cassava leaves as a protein source and ensiled cassava root as energy source. In: Making better use of local use feed resource (T.R Preston and R B Ogle, editors). University of Agriculture and Forestry, Thu Duc, Ho Chi Minh City pp 8)

Eeckhout W, Fontaine G and Deschriver R 1983 Energy value of vegetable fats for pigs and poultry. In: Fat quality in lean pigs. Meat Research Institute Special Report No. 2 p 88-97

Frank G R, Aherne F X and Jensen A H 1983 A study of relationship between performance and dietary component digestibility by swine fed different levels of dietary fibre. Journal of Animal Science 57:645-654

Gómez G G 1991 Use of cassava products in pigs feeding. Pig News and Information 12:387-390

González D A, González C, Díaz I, Ly J andVecchionacce H 1999  Determinación en cerdos de la digestibilidad de nutrientes de dietas de follaje de yuca amarga (Manihot esculenta Crantz) y aceite de palma (Elaeis guineensis Jacq.) Revista Computadorizada de Producción Porcina 6(1)22-30

Goering H K and Van Soest P J 1970 Forage fibre analyses (apparatus, reagents, procedures and some applications). USDA Agricultural Handbook No.379. ARS, Washington DC pp 19

Institut National de la Recherche Agronomique  1984 L’alimentation des animaux monogastriques: porc, lapin, volailles. INRA, Paris pp 282

Just  A 1983. The role of the large intestine in the digestion of nutrients and amino acid utilization in monogastrics. In: Int. Symp. Protein metabolism and nutrition, 05-09 September, Clermont-Ferrand. INRA, pp. 289-309

Just A, Fernández  J A and Jorgensen H 1983 The net energy value of diets for growth in pigs in relation to the fermentative processes in the digestive tract and the site of absorption of teh nutrients. Livestock Production Science 10:171-186

Just A, Jorgensen H and Fernandez J A 1981 The digestive capacity of the caecum-colon and the value of the nitrogen absorbed from the hind gut for protein synthesis in pigs. British Journal of Nutrition 46:209-217

Kass M L, Van Soest P J and Pond W G, 1980 Utilization of dietary fiber from alfalfa by growing swine. Journal of Animal Science 50:192-197

Kennelly J J and Aherne F X 1980 The effect of fiber formulated to contain different levels of energy and protein on digestibility coefficients in swine. Canadian Journal of Animal Science 60:717-726

Kennelly J J, Aherne F X and Lewis A J 1978 The effect of levels of isolation, or varietal different in high fiber hull fraction of low glucosinolate rapeseed meals on rat or pig performance. Canandian  Journal of Animal Science 58:743-752

King R H and Taverner M R 1975 Prediction of the digestible energy in pig diests from analyses of fibre contents. Animal Production 21:275-284

Kurival M S and Bowland J P 1962  Supplemental fat as an energy source in the diets of swine and rates. II. Energy and nitrogen digestibility, nitrogen retention and carcass fat composition . Canadian Journal of Animal Science 17:1115 (Abstract)

Leibbrandt V D 1995. Effect of fat on performance of baby and growing pigs. Journal of Animal Science 40:1081-1085

Le Duc Ngoan 1994  The use of African palm (Elaeis guineensis) oil as an energy source for pig. MSc Thesis Swedish University of Agricultural Science. Uppsala pp 73

Li D F, Thaler R C, Nelssen J  L, Harmon D L, Allee G L and Weeden T L 1990  Effect of fat sources and combinations on starter pig performance, nutrient digestibility and intestinal morphology. Journal of Animal Science. 68:3694-3704

Ly J and Samkol P 2001  The nutritive value of ensiled cassava leaves for young Mong Cai pigs fed high levels of protein. Livestock Research for Rural Development 13(4):

Limon R L 1992 Ensilage of cassava products and their use as animal feed. In: Roots, tubers, plantains and bananas in animal feeding (D Machin and A W Speedy, editors). FAO Animal Production and Health. Paper No 95 Rome p 99-110


Morgan C A, Whittemore C T and Cockburn J H D 1984 The effect of level and source of protein, fibre and fat in the diet on the energy value of compounded pig feeds. Animal Feed Science and Technology 11:11-34

Nehring K and Haenlein G F W 1973 Feed evaluation and ration calculation based on net energy fat Journal of Animal Science 36:949-964

Nguyen Van Lai and Rodriguez L 1998 Digestion and N metabolism in Mong Cai and Large White pigs having free access to sugar cane juice or ensiled cassava root supplemented with duckweed or ensiled cassava leaves. Livestock Research for Rural Development 10(2):

Nguyen Thi Loc, Nguyen T H L, Vo T K T and Hoang N D 2000 Ensiling techniques and evaluation of cassava leaf silage for Mong Cai sows in Central Vietnam. In: Sustainable livestock production on local feed resource (T R Preston and R B Ogle, editors). Ho Chi Minh City p 25-29

Noblet J and Perez J M 1993  Prediction of digestibility of nutrient and energy values of pig diets from chemical analysis. Journal of Animal Science 71:3389-3398

Pratridge  I G,  Hel H D and Mitchell  K G  1982 Utilization of dietary cellulose by growing pigs. Anim. Prod. 35, 209-214

Preston T R. Rodriguez Lylian and Khieu Borin 2000. Association of cassava and legume tree as perennial forage crop for livestock. Workshop-seminar (making better use of local feed resource) January, 2000. SAREC-UAF (Editors: T R Preston and R B Ogle). UAF, Ho Chi Minh City, Vietnam

Perez J M 1991 Interet et limites des modeles de prevision de la valeur energetique des aliments destinés au porc. Thèse Doctorat. Université Montpellier II pp 196

Pettigrew J E and Moser R 1991 Fat in swine nutrition. In: Swine Nutrition.. Butterworth-Stoneham p 133

Pech Sovanno, Ly J, Pok Samkol and Preston T R 2002 Digestibility studies in growing pigs fed diets based on Cambodia rubber seed and soybeans supplement with water spinach ad libitum. Livestock Research for Rural Development. 14(6):

Pond W G,  Lowrey R S and Maner J H  1962  Effect of crude fibre level on ration digestibility and performance in growing-finishing swine. J. Anim. Sci. 21, 692-696.


Ravindran V 1990 Feeding value and digestibility of cassava leaf meals for growing pigs. In: Proceedings of the Fifth Australasia Animal Production Congress.  3:20

Ravindran V, Kornegay E and Rajaguru E S 1987 Influence of processing methods and storage time on the cyanide potential of cassava leaf meal. Animal Feed Science and Technology 17:227-234

Ravindran V and Ravindran G 1988 Changes in the nutritional composition of cassava (Manihot esculenta Crantz) leaves during maturity. Food Chemistry 27:299-239

Sandoval R A, Nielsen T K and Sorensen P H  1987  Effect of fibre on time of passage in pigs Acta  Agriculturae Scandinavica 37:367-373

Sauer W C, Just A, Jorgensen H H, Fekadu M and Eggum B O 1980  The influence of diet composition on the apparent digestibility of crude protein and amino acid at the terminal ileum and overall in pigs. Acta Agriculturae Scandinavica. 30:449-459

Sauer W C, Mosenthin R, Ahrens F and Den Hartog LA 1991 The effect of source of fiber on ileal and fecal amino acid digestibility and bacterial nitrogen excretion in growing pigs. Journal of Animal Science 69:4070-4076

Schneeman B O 1978  Effect of plant fibre on lipase, trypsin and chymotrypsin activity. Journal of the  Food. Science 43:634-636

Steel R G D and Torrie J A 1980  Principles and Procedures of Statistics: a Biometrical Approach McGraw-Hill Book Company (second edition) Toronto pp 663

Tewe O O 1992 Detoxification of casava products and effecs of residual toxins on consuming animals. In: Roots, tubers, plantains and bananas in animal feeding (D. Machin and S. Nyvold, editors) FAO Animal Production and Health Paper No 95. Rome p 81-98

Undersander D, Mertens D R and Theix N 1993. Forage analysis procedures. National Forage Testing  Association. Omaha pp 154

Van Soest P J, Robertson J B and Lewis B A 1991. Methods for dietary fiber, neutral  detergent fiber and non starch polysaccharides in relation to animal nutrition. Journal of Dairy Science 74:3583-3593

Whittemore C T 1993 The Science and Practice of pig Production. Longman Scientific & Technical, Longman Group UK Limited. . pp 637

Whittemore, C T 1998 The science and practice of pig production, 2nd ed. Blackwell Science, Oxford.

Zebrowska T 1973 Digestion and absorption of nitrogenous compounds in the large intestine of pigs. Rozniki Nauk Rolnicky B95:85-90


Received 21 May 2003; Accepted 1 July 2003 

 Back to top