Mimosa pigra for growing goats in the Mekong Delta of Vietnam
 

Nguyen Thi Thu Hong, Vo Ai Quac,^* Tran Thi Kim Chung, Bach Van Hiet, Nguyen Thanh Mong and Phan The Huu

Department of Animal Husbandry & Veterinary Medicine,
Angiang University, Vietnam
ntthong@agu.edu.vn
* Agriculture and Fisheries Export – Import Company (AFIEX),
1234/63 Tran Hung Dao, Long Xuyen, An Giang, Vietnam

Abstract

Studies were made on: (i) effect of harvesting frequency on biomass yield and composition of Mimosa pigra; and (ii) growth rates of goats fed mimosa foliage under grazing conditions or in confinement.  Experiment 1 was a completely randomized design comprising 4 harvest frequencies of 30, 45, 60 and 90 day intervals with 6 replications. In Experiment 2a, goats were fed in metabolism cages on Mimosa as the sole diet or supplemented with Para grass. In Experiment 2b, the treatments in an on-farm trial were day-time grazing of Mimosa or feeding it in confinement, in each case with or without access to Para grass in the night-time.

Biomass yields of DM and crude protein showed a curvilinear relationship with harvest interval with maximum values for the 60 day interval. Content of crude protein in the leaves decreased linearly with harvest interval while condensed tannins increased. For optimum nutritive value, the 45 day harvest interval appeared to be the best, with 14% crude protein and 4% condensed tannins in the DM of the leaves. Growth rates of goats on a sole diet of Mimosa foliage were 81 g/day in confinement and 98 g/day under free grazing, with no additional benefit for supplementation with Para grass.

The excellent growth rates in both experiments with Mimosa as the sole feed implies that the foliage is providing adequate amounts of both rumen fermentable and “bypass’ protein.

Key words:  Biomass yield, confinement, digestibility, feed intake, grazing, grass supplement, growth, tannins

Introduction

. This plant is considered to be one of the worst environmental weeds of the Mekong River basin (Storrs et al 2001). In Tram Chim National park in Dongthap Province in the Mekong delta, there is growing concern over the rapid growth of the Mimosa pigra plant, that has taken over more than one seventh of the 7,600 ha of the park ((Tran Triet et al 2007).  An alternative approach to control by conventional methods, is to consider it as a potential feed resource so that it can yield economic benefits in areas where it is already established. When it was fed to sheep at low levels as a supplement to Para grass (Brachiaria mutica)  (Vearasilp et al 1981), the Mimosa did not reduce digestibility of the feed and was considered as a high-protein feed component.

In this paper we report the results of: (i) an agronomic study to determine effects of harvest interval on biomass yield and composition; and (ii) trials to evaluate its nutritive value when fed as the principal component of diets for growing goats. 

Experiment 1.  Biomass production of Mimosa pigra

Material and methods

The trial was carried out in Dongthap Province, in an area where there was already a dense infestation of mimosa.

Treatments and design

The treatments in a randomized block design were 4 harvest frequencies of 30, 45, 60 and 90 day intervals, with 6 replications. Individual plots measuring 4 x 4 were marked out in the existing stand of mimosa, which had  16 to 20 plants / m^{2 ­­}(Photo 1).

Procedure

The plants were cut to 10 cm above ground level at the start if the trial. The harvest frequencies were then applied to the resultant re-growth, in each case cutting the plants at the same height of 10cm above ground level (Photo 2). At each harvest, the foliage was weighed fresh and a 200 g sub-sample taken from each plot taken and dried at 70^o C for 48 hours. The dried samples were pooled within replicates and the 6 samples per treatment were used for analysis of nitrogen and ash (AOAC 1990).

Statistical analysis

The data were analysed by the GLM option in the ANOVA software of Minitab (2000). Sources of variation were treatments, replicates and error. Relationships between the input variable (harvest interval) and responses (yield of DM and crude protein,  percentage of crude protein and tannins in leaves) were computed by linear and curvilinear regression using the same Minitab software. yield and by regression .

Results and Discussion

The DM yield response to increasing harvest interval was curvilinear reaching a maximum value with a harvest interval of 60 days followed by a steep decline to 90 days (Table 1 and Figure 1). Yield of crude protein as leaves showed a similar trend to DM (Figure 2). The content of crude protein in leaves decreased while the concentration of condensed tannins increased (Table 1 and Figures 3 and 4).

Experiment 2. Nutritive value of Mimosa pigra for growing goats

Experiment 2a. Growth and digestibility study on-station

This experiment was done at Angiang University. Eight goats were vaccinated against foot and mouth disease and de-wormed before the initiation of the experiment. They were individually fed in metabolism cages with free access to water during the trial period of 90 days.

Treatments and design

The two treatments in a completely randomized design (CRD) were:

·        MP: Mimosa pigra foliage as the only feed
·        MPG : Mimosa pigra foliage and Brachiaria grass

There were 4 replication (goats) of each treatment.

Feeds and feeding

Mimosa pigra and Brachiaria grass were tied in bunches and hung from the roof of the cage above the feed trough (Photo 3).

New feed was offered once daily at 09.00 h after discarding the previous day’s leftovers. The goats were weighed at 2-week intervals for 2 consecutive days. After 80 days of the experimental feeding a metabolism trial of 7 days duration was conducted on goats from each group in metabolism cages with provision for quantitative collection of faeces and urine. Pooled samples of feed offered and leftovers, and faeces and urine from the metabolism trial were subjected to preliminary processing and preserved for subsequent chemical analysis.

Measurements

DM was determined by drying at 100^oC for 24 h, organic matter (OM) by ashing at 550^oC for 4h and crude protein by the Kjeldahl technique (AOAC 1990). Neutral detergent fibre (NDF) was analysed using the method of Van Soest and Robertson (1985).

Statistical analysis

The data were analysed by the GLM option in the ANOVA software of Minitab (2000). Sources of variation were treatments and error.
 

Experiment 2b: Growth of goats grazing Mimosa pigra in infested area

This experiment was carried out on cooperative farms in Tram Chim National Park in Tam Nong District, Dong Thap Province in the Mekong Delta, Sixteen growing goats were divided into 4 farm households, and the design was a 2*2 factorial arrangement of four treatments:

G: Grazing of Mimosa pigra in the day time
GS: Grazing of mimosa in the day time and supplemented with grass at night
C: Confined, and feeding with 100% Mimosa pigra
CS : Confined, and feeding with Mimosa pigra and grass free choice

The animals were vaccinated against foot and mouth disease and de-wormed before the initiation of the experiment. For treatments C and CS, the Mimosa and grass were given fresh after being collected by the farmers, and were offered on an ad libitum basis by hanging bunches of the Mimosa and the grass on the pen wall, simulating the way traditionally used by the farmers. In treatments G and GS, grazing was from 8h to 11h in the morning and from 1h30 to 4h30 in the afternoon (Photo 4).  The rest of the time the goats were confined to the pens. In the night-time, goats on treatment CS had free access to Para grass offered as in treatment GS. Goats on treatment "C" received no supplementation in the night-time.

Photo 4. Goats grazing Mimosa (treatments G and GS in Experiment 3)

Measurements

Live weight was measured every two weeks, in the morning before grazing, over a period of 90 days. Growth rates were calculated from the linear regression of live weight on time (days). Intake of supplements was recorded every day and samples were retained for analysis of DM, nitrogen, NDF and ADF as in Experiment 2a.

Statistical analysis

The data were analysed by the GLM option in the ANOVA software of Minitab (2000). Sources of variation were management system (grazing or confinement), supplementation, the interaction of system*supplementation, blocks (farms) and error.

Results and discussion

Experiment 2a.

Data on the chemical composition of the mimosa and para grass are in Table 2.

 There were no differences between treatments in feed intake and coefficients of apparemt digestibility of DM, OM and crude protein (Table 3). There was an indication (P=0.??) that live weight gain was higher on the treatment with Mimosa as the sole feed (MP).

The results show that Mimosa pigra foliage can be the sole feed for goats in confinement with acceptable growth rates..

Experiment 2b:

Live weight gain was higher for grazing compared to confinement, with no advantage from supplementation with Para grass (Tables 4 and 5; Figure 5). There was no interaction between management system and diet.

14.0

The higher growth rates of goats grazing Mimosa compared with being fed the foliage in confinement could be due to increased opportunity for selection of the leaves, and their “freshness”, in the former system. The effect of supplementation with grass was different between Experiments 2a and 2b, with an indication of poorer growth rate when the Mimosa was supplemented with grass in the former and no difference in the latter experiment. However, conditions were different in that in Experiment 2a, the goats were confined individually in metabolism cages with restricted movement, while in Experiment 2b they were in a pen with greater freedom of movement.

The excellent growth rates in both experiments with Mimosa as the sole feed implies that the foliage is providing adequate amounts of both rumen fermentable and “bypass’ protein. The condensed tannin level of 4 to 5% in the DM of the “young” Mimosa foliage is the probable reason for the good rumen bypass characteristics.

Conclusions

• Biomass yields of DM and crude protein showed a curvilinear relationship with harvest interval with maximum values for the 60 day interval.

• Content of crude protein in the leaves decreased linearly with harvest interval while condensed tannins increased.

• For optimum nutritive value, the 45 day harvest interval appeared to be the best, with 14% crude protein and 4% condensed tannins in the DM of the leaves.

• Growth rates of goats on a sole diet of Mimosa foliage were 81 g/day in confinement and 98 g/day under free grazing.

Acknowledgments

We wish to thank the Mekarn Project and Angiang University for allowing us to pursue this study. Thanks are also given to leaders and farmers of Tram Chim National Park, who created good conditions and assisted  us throughout the experiment.

References

AOAC 1990. Official Methods of Analysis, 15^th Edition. Association of the Official Analytical Chemists, Washington D.C.

Minitab 2000 Minitab Reference Manual, Release 13.1 for Windows. Minitab Inc., USA.

Storrs M, Ashley M, Tran Triet and Chin Samouth 2001 Towards the Development of Strategic Weed Management for the Lower Mekong Basin: a Report on A Training Workshop (Juliana Hotel, Phnom Penh, Cambodia, 6–8 November 2001)

Tran Triet, Le Cong Kiet, Nguyen Thi Lan Thi and Pham Quoc Dan  2007 The invasion by Mimosa pigra of wetlands of the Mekong Delta, Vietnam. [on-line]. Available from:  http://www.ento.csiro.au/weeds/pdf/mimosa_symposium/07Trietetal.pdf

Van Soest P J and J B Robertson 1985 Analysis of forages and fibre foods. A Laboratory Manual for Animal Science. Department of Animal Science. Cornell University. Ithaca, New York.

Vearasilp T, Potikanond N and Rajja-Apai P 1981 Mimosa pigra in sheep rations. Thai Journal of Agricul­tural Science, 14, 311–317.

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