Nutritive evaluation of tropical tree leaves for pigs. 
Flemingia (Flemingia macrophylla) 

Pok Samkol and J Ly 

University of Tropical Agriculture Foundation
Royal University of Agriculture
Chamcar Daung near Phnom Penh, Cambodia
samkol@uta.edu.kh and jlyca@yahoo.com

 Abstract

The nutritive value of flemingia (Flemingia macrophylla) leaf meal was assessed in two experiments with four Mong Cai castrate male pigs in each experiment, according to a balanced change over design for two treaatments. The flemingia leaf meal was obtained by separating leaves and petioles from branches harvested periodically (60 days on average). Leaves and petioles were sun-dried, ground and the resulting foliage meal (N 3.13; NDF 67.2% DM basis) incorporated in a basal diet of sugar palm (Borassus flabellifer) syrup and dried fresh water fish (15 and 30% of substitution by Flemingia leaf meal).

Faecal output of fresh material and water was greatly increased (P<0.001) with increasing levels of dietary flemingia leaf meal. At the same time a decrease in faecal pH values and DM concentration was encountered. Similarly, faecal ammonia and SCFA output were highest (P<0.001) when pigs were fed 30% of flemingia leaf meal.

Dry matter, organic matter and N digestibility of the diet were significantly depressed (P<0.001) with increasing levels of flemingia leaf meal in the diet. NDF digestibility was rather low in treatments containing 15 and 30% of flemingia leaf meal (overall mean, 27.7%). N retention of the diet showed a high variability amongst animals and did not appear to be greatly influenced by graded levels of flemingia leaf meal in the diet.

In vitro pepsin/pancreatin digestibility of N from flemingia leaf meal was 19.8 % in accordance with in vivo digestibility results. In vivo organic matter and N digestibility as determined by difference (n = 8) revealed a low nutritive value of flemingia leaf meal for pigs (25.3 and 21.7% respectively).

The use of flemingia leaf  meal in diets for pigs could be justified if methods to increase its nutritive value could be successfully carried out.

 Key words: pigs, flemingia leaves, Flemingia macrophylla, digestibility

 
Introduction

It has been suggested that flemingia (Flemingia macrophylla) could be a useful legume specie in animal production (Gutteridge 1994; Djogo et al 1995). In this connection, in America, Botero and Russo (1999) have included flemingia in the list of main N-fixing trees and shrubs that could be employed in living fodder banks to be used for livestock.

Flemingia is an erect, woody shrub of Asiatic origin, with trifoliate leaves. The habitat of flemingia has been studied by Budelman (1989) in Indonesia, and it has been reported that flemingia is a hardy shrub that can resist either long dry periods or slight flooding conditions. On the other hand, it has been claimed that flemingia can tolerate acid, infertile soils rich in soluble aluminium (Budelman 1989). In fact, Djogo et al (1995) have suggested that flemingia may be a good agent for rehabilitation of acid, infertile soils.

There are conflicting reports concerning average flemingia foliage yields. In this connection, Gutteridge (1990) found yields of 125 g/plant in Queensland. However, it has been argued that average flemingia yield is high: 418 g DM/tree, from which 71% could be leaves (Nurjaya et al 1991). In this connection, Nurjaya et al (1991) have indicated that average DM yield of flemingia is lower than gliricidia (793 g/tree from which 65% was leaves), but considerably higher than Sesbania grandliflora (215 and 59%) and Leucaena leucocephala, cv Cunningham (51 and 74%). Flemingia yields have been reported to be 12.4 tonnes DM/ha with four cuts per year in plantations with a population of 10⁴ plants/ha.

Flemingia has been evaluated in intercropping farming systems (Yamoah et al 1986) and it has been suggested that this legume can be used for elimination of weeds in alley cropping, aiding to moisture retention in soil, and as green manure source, due to its slow breakdown (Gutteridge 1994; Djogo et al 1995).

As compared to ruminant feeding and nutrition, very little is known about pigs fed with flemingia (D’Mello 1992). The objective of this article is to report data on the nutritive value of flemingia leaf meal given to young growing pigs.

Materials and methods

 General

The nutritive value of flemingia (Flemingia macrophylla) leaf meal was assessed in two experiments with four Mong Cai castrate male pigs. The flemingia leaf meal was obtained by defoliation of existing plants managed with periodical harvesting (60 days on average). Freshly cut leaves and petioles had 41.8 % DM and represented 60.9 ± 2.8 % of the entire foliage, as determined in a sample of ten branches. The leaf:petiole ratio was 6.4 ± 1.0 (fresh  basis).

Leaves and petioles were sun-dried, ground and the resulting foliage meal (N = 3.13 % in DM; NDF 67.2% in DM) was incorporated in a basal diet of sugar palm (Borassus flabellifer) syrup and dried fresh water fish at levels of 15 and 30% substitution (DM basis). The sugar palm syrup was diluted with water (1:1 by weight) for facilitating the mixture with the other components of the diet.

 In vivo studies

Two in vivo digestibility trials were conducted to study the nutritive value of flemingia leaf meal. Four Mong Cai male castrate pigs of 18 kg average live weight were used in each trial, designed as a balanced change over design (Gill and Magee 1976; Gill 1978) with two treatments; Control and Flemingia. In Experiment 1 the level of flemingia leaf meal was 15% (FM15) while in Experiment 2 it was 30% (FM30). The same control diet was used in both experiments. The schedule of treatments and periods for experiment 1 is shown in Table 1. In experiment 2, the design was the same but with FM30 instead of FM15

The animals were housed in metabolism cages as described previously (Chiev Phiny and Rodriguez 2001). Every experimental period consisted of ten days, of which the first five days were for adaptation to the diets, and the last five days for quantitative collection of faeces and urine, as reported elsewhere (Ly et al 2001). Feed intake was fixed at 30 g DM/kg live weight and water was available ad libitum. The average environmental temperature during the trials was 32 ± 2.3 ^oC at 12:00 hr.

The composition of the experimental diets is listed in Table 2.

Samples of fresh faeces and feeds were dried at 100 ^ºC then ignited in a furnace at 500 ^ºC to determine organic matter content. The DM content was determined using the microwave method of Undersander et al (1993). Samples of feeds and faeces were analyzed for NDF (Van Soest et al 1991) and total N by a Kjeldahl method (AOAC 1990). In addition, fresh faeces were analyzed for pH according to a procedure described by Ly et al (2001). Faecal short chain fatty acids (SCFA) and ammonia were assayed after steam distillation of filtered faecal slurry (1:4 by weight) as outlined by Ly et al (2001). 

Nutrient digestibility and N balance coefficients were estimated by the conventional method and thereafter the nutritive value of flemingia leaves meal was calculated by difference (Crampton and Harris 1969). 

In vitro studies

Sun-dried samples of flemingia leaves were reground before incubation in vitro according to the method of Dierick et al (1985). Samples were subjected to a pepsin/HCl digestion at 39 ^ºC during 4 h followed by another 4 h digestion with pancreatin dissolved in phosphate buffer (pH 6.5). Total weight of substrate in each incubation flask was approximately 0.3 g DM and each incubation was carried out in quadruplicate. Ground, dried samples of fresh water dry fish and casein were incubated similarly. The analytical procedures applied to the residues after incubation were the same utilized in the in vivo experiment.

Data analysis

Data were processed using the software package MINITAB (Ryan et al 1985) and the analysis of variance was conducted by the recommended techniques (Steel and Torrie 1980). In both in vivo experiments, the nutritive value of the flemingia leaves were compared by the paired t-test, whereas in the in vitro experiment, means from every treatment were contrasted by a one-way classification procedure. In the required cases, the Duncan’s new multiple range test (Steel and Torrie 1980) was employed to discriminate significant differences among samples.

Results and discussion

General

The mixture of sugar palm syrup plus the dry ingredients, flemingia leaf meal included, was readily consumed by the animals, with no refusal in any case. During the in vivo studies, animals exhibited good health and no symptoms of discomfort were observed. All animals were in positive weight balance. 

Faecal status

Faecal ouput of fresh material and water was greatly increased (P<0.001) with increasing levels of dietary flemingia leaf meal (Table 3). At the same time a decrease in faecal pH values and DM concentration was encountered. Similarly, faecal ammonia and SCFA output was highest (P<0.001) when pigs were fed 30% of flemingia leaf meal.

The increase in faecal ouput has been observed in pigs fed increasing levels of fibrous materials. In this connection, Bach Knudsen and Hansen (1991) found that fibre was the most important factor influencing bulking characteristics of digesta. The increase in faecal bulking is in direct correspondence with an increase in water output, and it is probably dependent on the water holding capacity of the fibrous material. In this connection a decrease in faecal DM concentration is another immediate reflection of an increase in dietary fibrous levels, as this was the case in the present experiments.

It is well known that the large intestine of pigs is the site where an intense fermentative activity can occur (Vervaeke et al 1989; Jorgensen et al 1996), and compared with other sections of the gastrointestinal tract, the concentration of end products can be substantially higher (see for example Back Knudsen and Jorgensen 2001) as a direct consequence of bacterial activity. This appeared to be the case for SCFA and, therefore, the possibility of an increase in faecal excretion of SCFA could not be overlooked, as did take place in the present experiment.

The ammonia molecule can be either absorbed through the large intestinal wall (Zebrowska 1973; Just et al 1981) or used as elemental substrate for bacterial amino acid synthesis in the caecum and colon (Sauer et al 1991). Therefore faecal ammonia output must be a reflection of a balance between these two routes of ammonia utilization (Varel et al 1984). However, a clear interpretation of the causes of an increase in ammonia output in the faeces of the pigs is not apparent (Varel et al 1984). Perhaps a rather simple approach, to the status of faecal ammonia in pigs fed graded levels of fibrous materials, could be a consequence of an increased rate of passage of digesta through the gastrointestinal tract, caecum and colon included. This last hypothesis could be valid for pigs fed flemingia leaves, with a high concentration of cell wall in the plant biomass. 

 In vivo digestibility studies

Dry matter, organic matter and N digestibility of the diet were significantly depressed (P<0.001) with increasing levels of flemingia leaf meal in the diet (Table 4). NDF digestibility was very low in treatments containing 15 and 30% of flemingia leaf meal (overall mean 27.7%). N retention of the diet showed a high variability amongst animals and did not appear to be greatly influenced by graded levels of flemingia leaf meal in the diet. 

Djogo et al (1995) have suggested that the high fibre content of flemingia, and therefore, a low digestibility of nutrients, is a limitation for the use of this legume. Fasler (1993) found that with increasing incorporation of flemingia in the feed, faecal excretion of N increased in goats, with a concomitant depression of DM and fibre digestibility. The flemingia used by Fasler (1993) contained 2.51% condensed tannins. Other results obtained by Powell et al (1995) with sheep fed on graded levels of flemingia, indicated a decrease in the N duodenal flux and faecal excretion.  

It is well known that in the pig, an increase in dietary cell wall decreases in different degrees the availability of nutrients (see for example, Fernandez and Jorgensen 1986; Mathers 1990; Bach Knudsen and Jorgensen 2001). On the other hand, much of the non-starch polysaccharides (NSP) are included in the NDF fraction, and some NSP provoke an increased viscosity in intestinal digesta and a decrease of digestibility of NSP, N and energy (see for example, Yin et al 2001). In this connection, it is probable that the characteristics of the cell fractions of flemingia leaves could be the origin of the animal response. 

The nutritive value of flemingia leaves meal was rather low (Table 5). In fact, in vivo organic matter and N digestibility as determined by difference (n = 8) revealed a low nutritive value of flemingia leaf meal for pigs (21.7 and 25.3% respectively). It appears that the low digestibility values for pigs as those found for flemingia leaves are not quantitatively different from results with other legume trees and shrubs leaves, as has been observed for leucaena (Ly et al 1998) and desmanthus (Ly and Pok Samkol 2001). 

 In vitro digestibility studies

In vitro pepsin/pancreatin digestibility of N from flemingia leaf meal was 19.8 % (Table 6) in accordance with in vivo digestibility results. As to be expected, there were significant differences (P<0.001) between flemingia leaf meal and dry fresh water fish in in vitro digestibility of DM, organic matter and N. Lascano et al (1995) have observed in ruminants that crude protein and tannin content in flemingia foliage are rather high, and that in vitro DM digestibility is below 40% for ruminant animals. In this connection, Asare (1985) has reported that in vitro DM digestibility for ruminants was less than 40% but that palatability of young immature pods was adequate and considerably higher than old leaves. 

 Conclusions

The most important implication arising from this experiment is that flemingia leaf meal should not be employed in any pig feeding system, at least at levels as high as 15% in the diet. The use of flemingia leaf meal in diets for pigs could be justified if methods to increase its nutritive value could be successfully carried out.
 

Acknowledgments

This publication is an output from a collaborative project between the Swine Research Institute at Havana, Cuba, and the University of Tropical Agriculture Foundation, Phnom Penh. This project has been partially funded by FAO, Rome (certifying officer, Dr. Manuel Sanchez, AGAP). The technical assistance of Mr. Kim San Sophon (Royal University of Agriculture, Phnom Penh) and Mr. Hean Sopheap (Maharishi Vedic University, Prey Veng) during the conduct of the experiment is gratefully acknowledged. 
 

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