Biomass production and feed quality of multi-purpose trees

Nguyen Phuc Tien, Nguyen thi Mui, Dinh Van Binh and T R Preston¹

Goat and Rabbit Research Centre, Sontay, Vietnam

Abstract

This paper reports preliminary observations on some multi-purpose trees the leaves of which can be used as animal feed. Four species: Mulberry (Morus alba), Flemengia congesta, Bananas (Musa spp), Trichantera gigantea and Jack fruit (Artocarpus heterophyllus) were established in plots with soil pH of between 4.3 and 5.3. Trichantera gigantea was planted from 1993 to 1995 in pure stand and bananas in pure stand in 1994–1995. Based on recorded data after two years, new plots were established in which the two crops were associated with the bananas providing shade for the Trichantera gigantea. Plots of Flemengia congesta and mulberry (Morus alba) were planted in 1994 in soil of pH 4.3 to 4.5. Data on Jackfruit were recorded for individual trees which had been planted 10 years ago at the station. Trees of approximately the same age in 10 farm households close to the Centre were also recorded.

Flemengia congesta produced annually four times more dry matter (13.4 vs 3.94 tonnes/ha) and protein (2.24 vs 0.67 tonnes/ha) than mulberry. Trichantera gigantea produced 66 and 98 tonnes of fresh forage/ha in the second and third year after planting, equivalent to 8.6 and 12 tonnes dry matter and 1.3 and 1.8 tonnes protein/ha. When grown in association with bananas fruit yield of banana in the first year was not reduced (17.8 and 16.3 tonnes/ha, in pure and mixed stand) but there was an additional production of 20 tonnes of foliage from the Trichantera. Annual yield of leaves from 10-year old Jack fruit trees, defoliated at approximately 3-month intervals, was of the order of 150 to 250 kg/tree, equivalent to an annual yield of between 37 and 63 tonnes/ha fresh leaves (based on area per tree of 40m²), and a protein yield of 1.9 to 3.2 tonnes/ha/year.

Jack fruit leaves appear to be an excellent feed for goats while Trichantera gigantea and Flemengia congesta appear to have the most potential for rabbits. Cost of production per unit dry matter of forage was highest for mulberry but for Jack fruit, Trichantera gigantea and Flemengia congesta it was lower and the same as for Guinea grass and Elephant grass.

Key words: Multi-purpose trees, mulberry, Flemengia congesta, Trichantera gigantea, Jack fruit, banana, goats, rabbits, biomass, protein, associated crops

¹ Finca Ecologica, University of Agriculture and Forestry, Ho Chi Minh City, Vietnam
E-mail: thomas%preston%sarec%[email protected]

Introduction

Bavi district is located some 60 km North-west of Hanoi with an average slope of 3–8^o. The soil is of low fertility and the organic matter has been reduced to very low levels by erosion. Drought occurs frequently in the area. It is hilly land where there is big potential for developing animal husbandry especially goat and cattle production. From the early 1980's research at this Centre has been directed to improving the income of poor farmers in the area through animal husbandry development and finding animal feed resources with maximum output and minimum inputs.

Mulberry (Mora alba), bananas (Musa spp), Flemengia congesta and Trichantera gigantea are multipurpose trees. They are complementary sources of tropical biomass, providing protein to balance the carbohydrate in grass, sugarcane and food crop by products of low nutritive value (Preston and Murgueitio 1987, 1994). They are rich in minerals and vitamins and have multiple uses as fences, wind breaks, for construction and for fuel. Many species can fix atmospheric nitrogen and can be incorporated into grazing systems to protect the soil against erosion and stimulate nutrient recycling. They are long time members of the tropical flora and help to protect the environment.

In order to increase animal feed availability, not only for goat and rabbit production at this Centre, but also for developing feeding systems for farmers in Bavi district, evaluations have been made on the biomass production from multi-purpose trees which can be used as animal feed. The objectives were to identify those trees which can give high biomass production, have high nutritive value and provide feed throughout the year.

Materials and methods

Biomass production
Four species: Mulberry (Morus alba), Flemengia congesta, Bananas (Musa spp), Trichantera gigantea and Jack fruit (Artocarpus heterophyllus) were established in plots with soil pH of between 4.3 and 5.3. Trichantera gigantea was planted from 1993 to 1995 in pure stand and bananas in pure stand in 1994–1995. Based on recorded data after two years new plots were established in which the two crops were associated, with the bananas providing shade for the Trichantera gigantea. Plots of Flemengia congesta and mulberry (Morus alba) were planted in 1994 in soil of pH 4.3 to 4.5.

Table 1: Yields of fresh and dry biomass and of protein of Mulberry and Flemengia congesta grown in adjacent plots

Data on Jack fruit were recorded for individual trees which had been planted 10 years ago at the station. Trees of approximately the same age in 10 farm households close to the Centre were also recorded for two harvests to measure leaves and fruit production.

Mulberry, Flemengia congesta and Trichantera gigantea were harvested by cutting the stems at 70 cm above soil level at intervals of approximately 3 months with the first harvest at about 5–6 months after planting. For Jack fruit, branches were “lopped” and the stems with attached leaves were separated from the branches and used as the forage.

Table 2: Biomass yield of bananas and Trichantera gigantec in pure stand and as association (mixture)

Animal trials
Feed intake studies were done with goats and rabbits to obtain data on the relative palatability of the leaves. The goats (n=5; average 20–30 kg liveweight) were fed a basal diet of guinea grass, rice straw, molasses-urea block and concentrates and had access to the test foliage in turn during ten day periods. Intake of the foliage was taken as the average over the last seven days. The rabbits (n=5; average liveweight 1.5 kg) were fed their standard diet of guinea grass and concentrates and received the test foliage over ten day periods of which the last seven were used for intake assessment.

Local costs of inputs and market prices of the various products were used to calculate the cost to produce 1 kg of feed for each species.

Results and discussion

Biomass production and quality

Mulberry and Flemengia congesta
Biomass production for mulberry and Flemengia congesta in the first and second years is shown in Table 1. Yields were low in the first year for both species but increased dramatically in the second year. Flemengia congesta yielded much more (four times) than mulberry in both dry matter and protein.

Table 3: Biomass yield from the jack fruit tree (trees were 10 years old both on-station and onfarm)

Trichantera gigantea

Trichantera gigantea is new in Vietnam having been introduced from the coffee growing areas in Colombia in 1991. It has adapted readily in a wide range of ecosystems in Vietnam from North (Nguyen Ngoc Ha and Phan Thi Phan 1995) to South (Nguyen Thi Hong Nhan et al 1996) and has been well received by farmers as it is relished by pigs and can be a substitute for the sweet potato tops traditionally fed as green “vegetable” to balance the rice bran (Nguyen Thi Loc et al 1997). It was planted in the Centre first as a pure stand and more recently in association with bananas as it has been observed that it grows much better under partial shade. Yield data from the plots grown in “pure stand” and those planted more recently as associations are shown in Table 2. The data are not strictly comparable as establishment was in different years, the plot sizes are different and the plots are some 100 m distant from one another. Nevertheless the observations are interesting as they indicate: (i) that fruit yield from the bananas is not affected by growing them in association with the Trichantera; and (ii) the total yield of forage is more than 30% greater and of a higher average protein content from the association of the two crops. The yields of forage from Trichantera gigantea are similar to those reported by Gomez and Murgueitio (1991) from Colombia.

Table 4: Chemical composition of components of the biomass of bananas, mulberry, jack fruit, T gigantea, and F congesta.

Jack fruit
Farmers in the hilly and mountain areas of Vietnam traditionally grow jack fruit trees in their home gardens primarily for the fruit because of its high nutritive value for the family and because it requires few inputs. The disadvantage is that it requires some 6 to 7 years before bearing fruit. However, during this time other crops can be grown in association. Vietnamese farmers know that the leaves are palatable and have a good nutritional value for goats and cattle, and that they are a medicinal food for sick animals. But there appears to be little documented information on biomass production when the trees are subjected to regular defoliation, or on performance of animals fed jack fruit leaves as a major component of the diet.

The observations in Table 3 show that annual yield of leaves from 10-years old trees, defoliated at 3-month intervals, is of the order of 150 to 250 kg/tree. Assuming a population of 250 tree/ha (based on area per tree of 40m²) this is equivalent to a fresh matter yield of between 37 and 63 tonnes/ha.

Table 5: Estimated cost of producing 1 kg of product (leaves or fruit in fresh form)

* Foliage
** Leaves only
#Managed as dualpurpose crop for fruit and leaves

Nutritive value
Data on dry matter, protein (N^*6.25) and crude fibre (Weende method) are given in Table 4. The dry matter content of jack fruit leaves is very high (33%), twice the value in mulberry (17%) and Trichantera (13%). Protein content is similar for all species (15 to 17% in dry matter). The fibre in Flemengia congesta is twice that in the other leaves.

Table 6: Relative intake of foliage of bananas, mulberry, jack fruit, T gigantea and F congesta by goats and rabbits

Applying these data to the yield figures in Table 3 we can estimate the yield of jack fruit leaves as dry matter: 12 to 20 tonnes/ha/year; and protein 1.9 to 3.2 tonnes/ha/year.

Estimated costs of producing the foliage are presented in Table 5. Mulberry was the most expensive forage (VND335/kg) to produce mainly because of low yield and higher weeding and harvest cost. The costs for the others, when fully established, were in the range VND 77 to 109/kg. Costs of producing guinea grass and elephant grass were reported by Nguyen Thi Mui et al (1992) to be 102 and 86 VND/kg, respectively. Thus the costs of producing the protein-rich foliage in this study (Trichantera gigantea, Flemengia congesta and Jack fruit), when fully established, were similar to those for grasses, but obviously the tree foliage are of much higher nutritive value.

Bananas integrated with T. gigantea, in the first year, gave 16,300 kg fruit/ha. If this had been sold directly in the local market at the prevailing opportunity price of 1000 VND/kg, the income would have been 9.5 million VND/ha, and the T. gigantea and banana foliage, plus the observed improvement in soil fertility, are additional benefits.

Feed intake studies
The relative intake by goats and rabbits of the different foliage are summarized in Table 6. Highest intake on dry matter basis for goats was with Jack fruit (960 g/day) and lowest was for banana stem (only 73 g/day). Flemengia congesta was eaten at the rate of 480 g/day and the other leaves in the range of 250 to 320 g/day. High intakes of jack fruit leaves and good growth in young goats (67 g/day) was observed by Keir et al (1996) in an experiment at this Centre; by contrast, performance on Trichantera gigantea was very poor (-65 g/day).

For rabbits, the highest intake of dry matter was on Flemengia congesta (77 g/day), followed by Trichantera gigantea (49 g/day) and mulberry (39 g/day).

Conclusions and recommendation
After 3 years of collecting and testing new species of forage plants at our station, it is possible to arrive at some tentative conclusions and recommendations:

• Bananas give very high biomass production and much more benefit when integrated with Trichantera gigantea in an associated crop-livestock system
• Trichantera gigantea and Flemengia congesta gave high yield and good quality and grow very well in the hilly land of Bavi district.
• Jack fruit leaves appear to be an excellent feed for goats
• Trichantera gigantea and Flemengia congesta appear to have the most potential for rabbits
• Cost of production per unit dry matter of forage was highest for mulberry but for Jack fruit, Trichantera gigantea and Flemengia congesta it was lower and the same as for Guinea grass and Elephant grass.

References

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