Effect of Mimosa pigra and water spinach (Ipomoea aquatica) on intake, digestibility and growth of goats in the Mekong delta, Vietnam

Nguyen Thi Thu Hong and Nguyen The Lam

Department of Animal Husbandry and Veterinary,
Angiang University, Vietnam
ntthong@agu.edu.vn

Abstract

The experiment was conducted on a farm in Tam Nong district, Dong Thap province to evaluate the feeding value of Mimosa pigra for goats. Sixteen growing male goats (16+3 kg live weight) were allocated to 4 treatments in a 2*2 factorial arrangement with 4 replications. The treatments were foliage of Mimosa fed fresh (MF) or wilted (MW); and with a supplement of water spinach (WS) or no supplement (NWS). The Mimosa foliage was offered ad libitum; water spinach was fed at 30 g/kg live weight (fresh basis). The trial lasted 110 days.  Growth rates were increased by feeding the fresh rather than wilted Mimosa (103 vs 91.7 g/day), and by supplementation with water spinach (102 vs 92.3 g/day) (SEM±4.7).  Feed intake and apparent digestibility coefficients for dry matter and crude protein showed the same tendency as growth rates. For the MFS and MWS treatments, water spinach represented 27% of the total DM intake.

Key words: Invasive weeds, legume, mimosine, tannins

Introduction

Mimosa pigra is a dangerous weed for crop production in Mekong Delta. However, farmers often make use of the foliage as feed for ruminant live stock. In the Yankari Game Reserve in Nigeria, it was reported (Geerling 1973) that Mimosa is a favored and stable part of the food supply for the larger herbivores. However, there have been conflicting reports on whether Mimosa contains the toxic amino acid, mimosine, which could restrict its use for animals. Vearasilp et al (1981a,b) reported that Mimosa did not contain mimosine, but it has been isolated at a level of about 0.2% of leaf dry weight by Lonsdale et al (1989).

In recent studies in the Mekong delta, Hong et al (2008) reported growing goats had weight gains of over 90 g/day when grazing exclusively on Mimosa. It was hypothesized that the relatively high levels of condensed tannins in the Mimosa leaves (5-9% DM) could confer bypass properties to the protein and thus enhance the growth rates on this feed.  However, too high levels of tannins in plants have been shown to reduce feed intake and growth rates (Reed 1995).   Kongmanila and Ledin (2009) reported positive responses in feed intake and N retention in goats when foliage from the Mango tree, rich in tannins, was supplemented with water spinach, the protein in which is known to be highly degradable by rumen microbes (Preston T R, unpublished data). Offering fresh water spinach at levels of 10 and 20 g DM per 1 kg live weight to goats having free access to fresh cassava foliage did not affect intake of the cassava with the result that total DM intake increased by 33 and 60%, respectively and digestibility of DM and crude fibre was also increased (Pathoummalangsy and Preston 2006).

It was therefore hypothesized that supplementing Mimosa foliage with water spinach would increase the digestibility of the diet and the growth rate of goats.

Materials and methods

Location

The experiment was done in a farm in Tam Nong district, Dong Thap province. Sixteen growing male goats (16+3 kg) were hired from small-holder goat keepers in the area. They were vaccinated against foot and mouth disease and de-wormed with Ivermectin before the start of the experiment. The goats were housed in individual metabolism cages with free access to water. The experiment lasted 110 days.

Treatments and design

The factors in a 2*2 factorial arrangement with 4 replications were:

Mimosa processing
    Fresh (F) or Wilted 24 h (W)

Supplement

    Water spinach at 30 g/kg live weight (fresh basis) (WS) or no supplement (NWS)

Feed management

The Mimosa foliage was from a field where the Mimosa was managed with a cutting interval of around 45 days. Water spinach was collected from natural stands in the area. The Mimosa foliage was wilted by placing the branches in the shade during 24 h. The offer level was 120% of the average daily DM intake of Mimosa the previous week. Water spinach was fed fresh at 30 g/kg live weight and was put in the feed trough. .The Mimosa was hung in bunches above the feed troughs (Photo 1).  Fresh feed was offered two times daily at 08:00  and 16:00.

Photo 1. Hanging the Mimosa foliage above the feed trough

Measurements

Feeds offered and refused were measured every day in the morning. The goats were weighed every 2 weeks. After 110 days of the experimental feeding a metabolism trial of 7 days duration was  conducted on each goat. Feed intake was fixed at 80% of the DM intake recorded the previous week. Pooled samples of feed offered, leftovers and feces from the metabolic trial were preserved at -18°C for subsequent chemical analysis.

Chemical analysis

DM was determined by drying at 100 °C,  organic matter by ashing at 550^oC for 4h and crude protein by the Kjeldahl technique (AOAC 1990).

Statistical analysis

The data from the experiment were compiled in the MS Excel software and analyzed using the general linear model  in the ANOVA program of the  Minitab (2000) software (release13.2). Sources of variation were: Mimosa processing, supplementation, interaction Mimosa*supplementation, replicates and error.

Results and discussion

Data on chemical composition of the feeds are presented in Table 1. The chemical composition of Mimosa included leaves, rachis and stem.

DM intake per unit live weight was increased when water spinach was fed and tended to be lower (P=0.19) when the Mimosa was wilted before feeding (Table 2; Figure 1). When water spinach was offered it accounted for 27% of the DM intake. Growth rates were increased when water spinach was fed and decreased when the Mimosa was wilted (Figure 2). DM feed conversion was not affected by the treatments.

Feed intakes during the digestibility trial showed the same tendencies as in the growth experiment (Table 3). Apparent digestibility of DM tended to be higher when water spinach was fed (P=0.10) and when the Mimosa was fed fresh rather than wilted (P=0.17) (Figure 3). There was a slight indication (P=0.23) that apparent digestibility of crude  protein was higher when water spinach was fed together with the Mimosa.

Figure 1: Mean values for DM intake as function of live weight  of goats fed Mimosa pigra fresh or wilted and supplemented with water spinach or not supplemented	Figure 2: Mean values for live weight gain by goats fed Mimosa pigra fresh or wilted and supplemented with water spinach or not supplemented

Figure 3: Mean values for apparent DM digestibility in goats fed Mimosa pigra fresh or wilted and supplemented with water spinach or not supplemented	Figure 4: Mean values for apparent crude protein digestibility in goats fed Mimosa pigra fresh or wilted  and supplemented with water spinach or not supplemented

The high growth rate when Mimosa was fed alone (98 g/day) or with water spinach (108 g/day) confirms the earlier report on the high nutritive value of this leguminous forage when fed to growing goats (Hong et al 2009). The improved performance when water spinach was offered at close to 30% of the diet DM was a similar response to that observed by Kongmanila and Ledin  (2009) when they added water spinach to forages of low digestibility. Pathoummalangsy and Preston (2006) studied the effect of two levels of fresh water spinach in a basal diet of cassava foliage. At the level of 27% of the diet DM, the feed intake, DM digestibility and N retention were increased by supplementation with water spinach. However, when the water spinach was given at the higher level of 40% of the diet DM,  there was a 350% increase in excretion of N in the urine with the result that N retention was reduced by 50% compared with the control diet without water spinach. 

Conclusions

• The live weight gain of goats was increased from 92 to 103 g/day by supplementing a sole diet of fresh Mimosa foliage with fresh water spinach at 27% of the total DM.

• Addition of water spinach to the diet increased the DM intake and tended to increase the DM digestibility.

• DM intake and live weight gain were reduced when the Mimosa was wilted with a suggestion that DM digestibility was also reduced.

Acknowledgments

The authors gratefully acknowledge the MEKARN Project, financed by Sida, and An Giang University for supporting this study. We also thank the Leaders and farmers of Tram Chim National Park for providing facilities and assistance to carry out the experiment.

References

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

Geerling C 1973 The Vegetation of Yankari Game Reserve: Its Utilization and Condition. Department of Forestry Bulletin 3. University of Ibadan, 49 pp.

Kongmanila Daovy and Ledin I 2009 Chemical composition of some tropical foliage species and their intake and digestibility by goats. Asian-Australasian Journal of Animal Science. 22 (6) 803-811  http://www.mekarn.org/msc2005-07/thesis07/Daovy.pdf

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Pathoummalangsy K and Preston T R 2006  Effect of a supplement of fresh water spinach (Ipomoea aquatica) on feed intake and digestibility in goats fed a basal diet of cassava foliage. Livestock Research for Rural Development. Volume 18 (3) from: http://www.lrrd.org/lrrd18/3/kham18035.htm

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

Received 9 June 2011; Accepted 19 June 2011; Published 1 July 2011

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