Some aspects of the nutritive value of leaf meals of
 Trichanthera gigantea  and Morus alba 
for Mong Cai pigs
 

J Ly, Chhay Ty, Chiev Phiny and T R Preston

 University of Tropical Agriculture Foundation
Royal University of Agriculture
Chamcan Daung, Dangkor District, PO Box 2423
Phnom Penh 3, Cambodia
julioly@uta.edu.kh

Abstract

The nutritive value for pigs of sun-dried leaves from trichanthera (Trichanthera gigantea) and mulberry (Morus alba) was assessed in two experiments. In experiment 1, digestibility indices and N balance were determined in eight Mong Cai castrated male pigs (mean liveweight 14.5 kg) fed 30% of sun-dried trichanthera or mulberry leaves according to a balanced change over design. In experiment 2, the in vitro (pepsin/pancreatin) N digestibility of both sets of leaf meals was compared. The substitution of 30% of the basal diet implied that both trichanthera and mulberry provided on average 31.3 and 37.1% of the total N in the diet.

In vivo organic matter and N total digestibility as estimated by difference were higher (P<0.01) in mulberry  than in trichanthera leaf meal (trichanthera, 71.5  and 66.2; mulberry 84.6 and 81.1%, respectively). The diet containing 30% of mulberry leaf meal exhibited a higher N retention (P<0.05) than that containing trichanthera leaf meal.

In vitro organic matter and N solubility, simulating ileal digestion in pigs, were higher (P<0.001) for mulberry as compared to trichanthera leaf meal (trichanthera 35.9 and 37.5; mulberry 56.7 and 47.7%,  respectively).

Further studies concerning factors affecting N utilization of trichanthera by pigs are recommended. The high nutritive value of the mulberry leaves employed in the present experiments indicates its potential as a protein source in pig feeding.

Key words: Trichanthera gigantea, Morus alba, Mong Cai pigs, nutritive value

Introduction 

In omnivorous animals such as pigs, the addition of substantial amounts of forages to the feed has largely been overlooked in the context of the protein supply from these resources. In this connection, tree leaves could be utilized to provide plant protein to pigs in the tropics, in a cut-and-carry system, since it is quite common to supply aquatic floating plant leaves and other fibrous crop by-products to local breeds of pigs in rural areas of several countries of the Far East (see for example, Le Mare 1952; Moore 1969).

In contrast to the well known deleterious effect of leguminous tree leaves on digestive and metabolic processes in monogastric animals (D’Mello 1992), non-leguminous trees seem to have advantages from the point of view of digestive physiology. In this connection, trichanthera (Trichanthera gigantea, Humboldt et Bonpland, Nees) and mulberry (Morus alba) could be included in the list of non-leguminous trees with a high potential as feed supplements for pigs (Rosales 1997; Sánchez 1999), among other monogastric animal species.

Trichanthera is a tree, native to South America, the leaves of which have been used in pig feeding with controversial results, perhaps due to the fact that its nutritive value is unknown as yet (Rosales 1997; Nguyen Thi Hong Nhan and Nguyen Van Hon 1999). On the other hand, it has been suggested that the use of mulberry tree leaves could be extrapolated from the traditional silkworm production in the Far East (see Tingzing et al 1988) to pigs  everywhere in the tropics (Sánchez 1999).

Several studies have been conducted on different aspects related to the agronomy and production of trichanthera and mulberry trees (Tinzing et al 1988) and their utilization in ruminant animals (see Benavides 1999; Rosales and Ríos 1999; Yao et al 2000). However, very little is known about the nutritional value of leaves from these trees in pigs.

The objective of the present communication is to report some initial studies related to the nutritive evaluation of trichanthera and mulberry leaves for pigs.

Materials and methods

General

Two leaf meals were prepared from trichanthera (Trichanthera gigantea) and mulberry  (Morus alba) trees harvested between February and March 2001, after a regrowth period of approximately 90 days, at the Ecological Farm plantation, in the Chamcar Daung Campus of the Royal University of Agriculture. As a general rule, tree crops in the farm are periodically fertilized with effluents originating from biodigestors charged with pig manure. The mulberry trees were of an unknown variety of Vietnamese origin. The trichanthera trees were also from Vietnam, where they had been introduced as stem cuttings from Colombia in 1992.

After harvesting, the leaves and petioles were separated from the branches and sun-dried before being ground in a hammer mill to produce the meal. The chemical composition of each leaf meal is presented in Table 1.

The nutritive value for pigs of sun-dried leaves from trichanthera and mulberry was assessed in two experiments. In Experiment 1,  in vivo total digestibility of nutrients and N balance were conducted in pigs, whereas in Experiment 2, the ileal digestibility of DM, organic matter and N was determined by in vitro incubation of the samples.

Experiment 1

Treatments and experimental design

 The experiment was conducted at Chamcar Daung, using 8 Mong Cai, castrated male pigs with mean body weight of 14.5 kg. The animals were housed in metabolism cages in which they could move freely (Chiev Phiny and Rodríguez 2001). The pigs received alternatively a basal diet comprising cassava bran, wheat bran and dried fresh water fish formulated to contain 16% crude protein (N x 6.25 in dry basis), or the same diet in which 30% of the diet was substituted either by trichanthera or mulberry leaf meal. The N contribution to total dietary N was 31.3 and 37.1% for trichanthera and mulberry leaf meal, respectively.

Cassava bran is a by-product of extraction of starch from cassava roots. It was obtained from small artisan producers in Kampong Cham province. Cassava bran was found to be high in NDF and very low in N (28.1 and 0.18% in dry basis, respectively). Dried fresh water fish was obtained in the Phnom Penh market and then ground to obtain a meal for mixing with the other ingredients of the diets. The dried fish was high in ash, crude fat and N (20.5, 18.0 and 6.68% in dry basis, respectively). The wheat bran was of unknown origin and had NDF 36.4 and N 2.79% in dry basis. The diets were given as a dry meal at a rate of 35 g DM/kg body weight per day at approximately 07:00 h each morning and refusals taken at 06:30 h the following day. Water was available ad libitum through drinking nipples.

The ingredients that were used and the chemical composition of each diet are presented in Table 2.

The four dietary treatments were imposed in a balanced changeover arrangement  (Gill and Magee 1976; Gill 1978) and were offered to the pigs over four ten-day periods. Measurements were made during the final five days of each period. The basal diet was given to the animals in periods 1 and 3, whereas this basal diet containing either trichanthera or mulberry leaf meal was supplied to the pigs in periods 2 and 4.

The details of faeces and urine sampling were as described by Ly et al (2001). Nutrient digestibility and N balance coefficients were estimated by the conventional method and thereafter the nutritive value of each leaf meal was calculated by difference (Crampton and Harris 1969). 

Chemical analysis of samples

To determine organic matter content, samples of fresh faeces and feeds were dried at 100 ºC then ignited in a furnace at 500 ºC. 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 the Kjeldahl method (AOAC 1990). Fresh faeces were analyzed for pH according to a procedure described by Ly et al (2001).

Experiment 2

In vitro analysis of samples 

Ground, dried samples of trichanthera and mulberry leaves were incubated in vitro according to the method of Dierick et al (1984). 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 cassava bran, wheat bran, fresh water 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 of MINITAB (Ryan et al 1985) and the analysis of variance was conducted by the recommended techniques, the variables being treatment, periods and error (Steel and Torrie 1980). In experiment 1, the nutritive value of the two leaf meals was compared by the paired t-test, whereas in experiment 2, 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 means. 

Results 

Experiment 1 

In general, all the animals gained weight during the trial, and there were no symptom of discomfort in the experimental pigs. At the end of the experiment, the average live weight was 23.3 kg. Feed refusals were very few and were more evident during the adaptation period. This was probably related to the increase in bulkiness of the diets, and the necessity of the animals to adapt to this circumstance. Average air temperature was 36.5 ± 2.5 ºC during the balance study. 

The analysis of variance showed no significant effect (P<0.05) of  period. On the other hand, no significant differences were observed in any measurement from both periods when the basal diet was offered to the animals. Therefore, data related to the basal diet were pooled and means are from 16 observations. Table 3 shows the data concerning total digestibility and N balance indices. 

There was no treatment effect on faecal pH, which was alkaline in all cases. The pigs consuming diets containing either trichanthera or mulberry  leaf meal tended (P<0.10) to have lower faecal DM than when they were fed the basal diet. 

It was found that the diet containing mulberry leaf meal had a higher (P<0.05) digestibility of DM and organic matter than the diet containing trichanthera leaf meal. There were no differences between the basal diet and the mulberry diets for these parameters.  In fact, the general trend was towards higher digestibility coefficients in pigs fed the diet with mulberry leaf meal. This was evident in N digestibility, and was more pronounced (P<0.05) in the data for dietary N retention, either expressed as percentage of N intake or of digested N. The reverse was true for pigs fed the diet with trichanthera leaf meal. Table 4 and Figure 2 show the comparison of the nutritive value of trichanthera and mulberry leaf meal per se. 

Figure 2: Digestibility indices for the leaf fractions of the diets
(calculated by difference)

Mulberry leaf meal had higher values (P<0.01) for all digestibility indices than trichanthera leaf meal. NDF digestibility indices were very variable, values, nevertheless the differences between the two leaf meals were significant.  

Experiment 2 

Data concerning the in vitro evaluation of the leaf meals other diet ingredients are listed in Table 5. 

In vitro organic matter and N solubility, simulating ileal digestion in pigs, were higher (P<0.05) for mulberry than for trichanthera leaves (trichanthera 35.9 and 37.5; mulberry 56.7 and 47.7%, respectively). As expected, the dried fish had the highest value (P<0.001) for  in vitro organic matter and N digestibility. Cassava bran had similar in vitro organic matter digestibility as trichanthera leaf meal, but lower values (P<0.001) for the in vitro N digestibility compared to the other diet ingredients.
 

Discussion

Trichanthera leaf meal

According to the results of the present experiments, there are some factors inherent to trichanthera leaves which prevent its efficient digestion by pigs. To our knowledge, there are no previous reports concerning studies of digestion of trichanthera leaves in monogastric animals, although several reports are available related to performance tests of either growing-fattening or breeding pigs (Sarría et al 1991; Sarría 1994; Nguyen Thi Hong Nhan and Nguyen Van Hon 1999). In Vietnam, the trichanthera tree has proved to be popular with farmers throughout the country with the leaves being fed to all classes of stock (Nguyen Thi Hong Nhan and Nguyen Van Hon 1999). This high rate of farmer adoption contrasts with the relatively poor digestive indices, especially of the nitrogenous fraction. It is possible that a certain fraction of the trichanthera leaves could be digested in the large intestine of pigs. Nevertheless, from the point of view of N economy, little profit will result from this direction, due to the fact that N disappearance from the large intestine of pigs is largely excreted in the urine (Zebrowska 1973).    

Gonzalvo et al (2001) examined several samples of leaves from Venezuela and found that the in vitro (pepsin/pancreatin) digestibility of organic matter and N was lower for trichanthera (28.8 and 30.2%) than for mulberry leaves (39.2 and 50.7%), thus following the same pattern of the present study. Gonzalvo el al  (2001) observed a high dependence of in vitro digestibility values on the cell wall content of the samples. Rosales (1997) found that trichanthera leaves contain very little water soluble N, and that the protein precipitating capacity was relatively high as compared to other tree leaves. It is possible that both of these factors could greatly contribute to the low digestibility values of trichanthera leaf meal in pigs, since Horigome et al (1988) observed a marked negative influence of polyphenol compounds on both in vitro and in vivo N digestibility in rats. 

Mulberry leaf meal

 As was predicted by Sánchez (1999), mulberry leaf meal appears to be a very promising alternative protein source for pigs in the tropics. Based on data arising from this study, it seems that pre-caecal digestion of substantial amounts of  mulberry leaf N takes place in pigs. To our knowledge, there are no previous reports concerning digestion of mulberry leaf meal in the pig, and therefore it is very difficult to establish any type of comparisons with data from other experiments. 

Methionine is deficient in mulberry leaf protein according to Machii (1989) and Yao et al (2000).  It appears from the results of the present study that the addition of dried fresh water fish to a pig diet containing mulberry leaf meal could be one way of providing the necessary sulphur-containing amino acids. In this connection, tropical countries such as Cambodia, where there is a ready availability of dried fish and where mulberry trees can be grown with high biomass yields, have considerable potential to develop sustainable pig production systems suitable for smallholder farmers. Further studies need to be conducted in order to establish the minimum amounts of fish protein necessary for an optimum utilization of the mulberry leaf meal.

 
Conclusions

·        Further studies are needed to identify the  factors affecting N utilization of trichanthera leaves by pigs.

·        The apparently high nutritive value of the mulberry leaf meal used in our study indicates that this feed resource has considerable potential as an alternative protein source in pig diets.

Acknowledgment

This publication is an output from a collaborative research project funded by FAO, Rome (Certifying officer, Dr Manuel Sanchez, AGAP).

 
References

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

Benavides J E 1999 Utilización de la morera en sistemas de producción animal. In: Agroforestería para la Producción Animal en América Latina (M D Sánchez and M Rosales, editors). Estudios FAO de Producción y Sanidad Animal 143, Rome p 275-281

Chiev Phiny and Rodríguez L 2001 Digestibility and N retention in Mong Cai pigs fed sugar palm (Borassus flabellifer) juice and ensiled fresh water fish. Livestock Research for Rural Development. 13(2): electronic version www.cipav.org.co/lrrd/lrrd13/2/phiny132.htm

Crampton E W and Harris L E 1969 Applied Animal Nutrition. The Use of Feedstuffs in the Formulation of Livestock Rations. Ed W H Freeman. San Francisco pp 753

Dierick N,  Vervaeke I, Decuypere J and Henderickx H 1985 Protein digestion in pig measured in vivo and in vitro. In: Proceedings of the 3^rd International Seminar on Digestive Physiology in the Pig (A Just, H Jorgensen and J A Fernández, editors). National Institute of Animal Science. Copenhagen p 329-332  

D’Mello J P F 1992 Nutritional potentialities of fodder trees and fodder shrubs as protein sources in animal nutrition. In: Legume Trees and other Fodder Trees as Protein Source for Livestock (A Speedy and P L Pugliese, editors) FAO Animal Production and Health Paper102, Rome p 115-127

Gill G L 1978 Change over design: sequence of treatments. Estimation of residual effects of treatments. In: Design and Analysis of Experiments in the Animal and Biological Sciences. Iowa State University Press. Ames 1:179

Gill G L and Magee W T 1976 Balanced two period change over design for several treatments. Journal of Animal Science 42:775-780

Gonzalvo S, Nieves D, Ly J, Macías M, Carón M and Martínez V 2001 Algunos aspectos del valor nutritivo de alimentos venezolanos destinados a animales monogástricos. Livestock Reearch for Rural Development 13(2): electronic version http://www.cipav.org.co/lrrd/lrrd13/2/gonz132.htm

Le Mare D W 1952 Pig rearing, fish farming and vegetable growing. Malayasian Journal of Agriculture 35:156-166

Ly J, Chhay Ty and Chiev Phiny 2001 Evaluation of nutrients of rubber seed meal in Mong Cai pigs. Livestock Research for Rural Development 13(2): electronic version www.cipav.org.co/lrrd/lrrd13/2/ly132.htm

Machii H 1989 Varietal differences of nitrogen and amino acid contents in mulberry leaves. Acta Sericologica et Entomologica. September:51-61

Moore A W 1969 Azolla: biology and agronomic significance. Botanical Reviews 35:17-34

Nguyen Thi Hong Nhan and Nguyen Van Hon 1999 Supplementing rice by products with foliage of Trichanthera gigantea in diets of growing and lactating pigs and fattening ducks. Livestock Research for Rural Development 11(3): electronic version www.cipav.org.co/lrrd/lrrd11/3/nhan113.htm

NRC 1998  Nutrient Requirement of Swine. National Academy of Science. 9^th edition. National Academy Press. Washington DC

Rosales M 1997 Avances en la investigación en el valor nutricional del nacedero (Trichanthera gigantea, Humboldt et Bonpland Nees). In: Arboles y arbustos forrajeros utilizados en la alimentación animal como fuente proteica. CIPAV. Cali p 127-144

Rosales M and Ríos C I 1999 Avances en la investigación en la variación del valor nutricional de procedencias de Trichanthera gigantea. In: Agroforestería para la Producción Animal en América Latina (M D Sánchez and M Rosales, editors). Estudios FAO de Producción y Sanidad Animal.143, Rome p 351-362

Ryan B F, Joiner B L and Ryan Jr T A 1985 Minitab (2^nd edition) Hilliday Lithograph

Sánchez M D 1999 Comentarios generales. In: Agroforestería para la Producción Animal en América Latina (M D Sánchez and M Rosales, editors). Estudios FAO de Producción y Sanidad Animal.143, Rome p 363-365

Sarría P 1994 Efecto del nacedero (Trichanthera gigantea) como reemplazo parcial de la soya en cerdas en gestación y lactancia recibiendo una dieta básica de jugo de caña. Livestock Research for Rural Development 6(1):62-73

Sarría P, Villavicencio E and Orejuela L E 1991 Utilización de follaje de nacedero (Trichanthera gigantea) en la alimentación de cerdos de engorde. Livestock Research for Rural Development 3(2):51-58

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

Tingzing Z, Yunfan T, Guangxien H, Huaizhong F and Ben M 1988 Mulberry cultivation. FAO Agricultural Series Bulletin 73/1. Rome pp 127

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

Yao J, Yan B, Wang X Q and Liu J X 2000 Nutritional evaluation of mulberry leaves as feeds for ruminants. Livestock Research for Rural Development 12(2): electronic version http://www.cipav.org.co/lrrd/lrrd12/2/yao122.htm

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

 Received 5 May 2001

Go to top