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 and 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); Viet Nam-VNS). 

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).

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).

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

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. 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 

Live weight was measured every two weeks, in the morning before grazing, over a period of 90 days. Intake of supplements was recorded every day and samples were retained for analysis of DM, nitrogen, NDF and ADF as in Experiment 2a.

The data were analysed using the GLM option of the ANOVA software in Minitab (2000). Sources of variation were: management, grass supplementation, interaction management*grass supplementation and errror.

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 apparent digestibility of DM and crude protein (Table 3). There was an indication (P=0.092) 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.

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 Toward 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 Robertson J B 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

Received 17 August 2008; Accepted 6 November 2008; Published 5 December 2008

Go to top