Effect on growth rate and digestibility in goats of supplementing a basal diet of mango foliage with fresh water spinach (Ipomoea aquatica)

Daovy Kongmanila, Kham Phommachanh and T R Preston*

National University of Laos,
daovyk@yahoo.com
* Finca Ecologica, UTA-Colombia, AA #48, Socorro, Santander, Colombia

Abstract

Two experiments were conducted to test the hypothesis that a supplement of water spinach would improve the nutritive value of a low quality foliage such as that from the Mango tree. In the first experiment, coefficients of apparent digestibility were determined with six male goats with initial body weight of 13 kg and around 3.5 months of age. The animals were allocated in a double 3*3 Latin-square design to treatments of Mango foliage alone  (M), Mango foliage + rumen supplement (MRS) and Mango foliage + water spinach (MWS). Each period consisted of 8 days of adaptation to the diets and 5 days of data collection. In the second experiment, fifteen male goats with initial live weight of 14 kg and around 4.5 months of age, were arranged in a randomized complete block design (RCBD) with five blocks and three treatments. The treatments were: Mango foliage + water spinach 0.5% of LW as DM (WS0.5), Mango foliage + water spinach at 1.0% of LW as DM (WS1.0); Mango foliage + water spinach 1.5% of LW as DM (WS1.5).

Supplementation of Mango foliage with water spinach, or with a mixture of urea/minerals (rumen supplement), improved the digestibility of crude protein and N retention in growing goats, but did not appear to affect DM digestibility. Increasing the level of water spinach as a supplement to Mango foliage from 15 to 36% (DM basis) for growing goats  led  to a linear increase in voluntary DM intake. Growth rate was increased by 25% as the intake of water spinach increased from 14 to 28% in the diet but subsequently declined to the same degree as the level of water spinach was raised from 28 to 36% of the diet DM. The poor growth performance of goats fed high levels of dietary water spinach is attributed to the diuretic effect of this plant with consequent negative impacts on protein and energy metabolism. It is concluded that goats fed foliages of low nutritive value such as Mango will improve their growth rates if given a supplement of water spinach at a level of 20 to 25% of the diet DM.

Keyword: Diuretic effect, intake, N retention, urine

Introduction

The mango tree (Mangifera indica), a multipurpose plant native to South Asia, is a potential source of foliage for ruminants since it is green all the year round. However,when the foliage was fed to growing goats as the sole diet it barely supported maintenance (Kongmanila et al 2007).  The low content of crude protein (69 and 47 g/kg DM in leaves plus petioles and stems, respectively according to Kongmanila et al 2007) appeared to be the main limiting factor as when the foliage was supplemented with protein-rich water spinach both digestibility and N retention were substantially increased (Kongmanila et al 2007).

The aim of the present study was to examine in more detail the effect of water spinach on the growth performance of goats fed a basal diet of mango foliage.

Materials and Methods

Location

The experiments were conducted in the farm of Livestock and Fisheries Department, Faculty of Agriculture, National University of Laos, 33 km south of Vientiane, Lao PDR. This area is tropical monsoon with a rainy season between May and October and a dry season from November to April. Average annual rainfall is 2000 mm/year.

Animals and management

Six male goats were used in the digestibility experiment, with body weights in the range from 12 to 14 kg and 3-4 months of age. They were housed in individual metabolism crates made from local materials measuring 0.8 x 0.8 x 0.8 m in width, length and height, respectively.  In the feeding trial, 15 local male were used in the experiment; their body weights were about 14 kg and were aged 4-5 months. Housing was similar to that used in the digestibility experiment but the dimensions were 1.0 x 1.0 x 1.0 m in width, length and height, respectively. The goats in both experiments were treated against parasites with injections of Ivermectin solution (1 ml per 4 kg body weight) and were vaccinated against Foot and Mouth disease, before starting the experiment.

 Treatments and design

The digestibility experiment was a double Latin square with 3 treatments, and 3 periods, each of 14 days (0-8 days for adaptation to the diets, 9-13 days for collection of faeces and urine.

The treatments were:

• M:  Mango foliage alone ad libitum;

• MRS: Mango foliage + rumen supplement (urea-minerals)

• MWS: Mango foliage + water spinach foliage

 In the feeding experiment, the goats were allocated to 5 blocks according to live weight. The 3 treatments (diets) were allocated within live weight blocks in a randomized complete block design (RCBD). The length of the trial was 12 weeks. Before the start of the experiment, the goats were adapted to the feed for 7 days. The treatments were:  

• WS0.5:  Mango + water spinach 0.5% of LW as DM

• WS1.0:  Mango + water spinach 1.0% of LW as DM

• WS1.5:  Mango + water spinach 1.5% of LW as DM

Feeds and feeding system

The rumen supplement (Table 1) was offered at 0.5% of live weight (DM basis) as a meal (all ingredients less the jackfruit leaves) in the feed trough. The Jackfruit leaves were mixed with the rest of the rumen supplement before being offered to the animals.

The mango foliage was given ad libitum with fresh foliage offered twice daily. The mango foliage was offered hanging, tied to a bamboo stick over the cage and above the feed trough to facilitate the collection of leaves that may have fallen down. Water spinach was offered the same way.

Measurements

In the digestibility trial, feeds offered and refused were recorded daily during the collection period. Six samples of each foliage were separated and weighed to estimate the average proportion of leaves plus petiole and stem. During the collection period the refusals were separated into leaves plus petiole and stem in order to measure the selection of the different parts.

During the data collection periods, the faeces and urine excreted were recorded twice daily at 7:00 h and 17:00 h. At each data collecting time, 10% of the faeces was sampled and frozen at –20^oC. Urine was collected in a jar containing 50 ml of 10% sulphuric acid (urine pH<3) to preserve the nitrogen (Chen and Gomes 1992). A sample of 10% of the urine was stored at 4^oC for further analysis.

In the feeding trial, feeds offered and refusals were recorded daily. Samples of feed offered and refused were taken weekly for analysis of DM. Pooled monthly samples were kept for further analysis. At the weeks: 0, 2, 4, 6, 8, 10, 12 the goats were weighed in the morning before feeding.

Fresh foliage was analyzed for DM, ash and CP according to the methods of AOAC (1990). NDF was determined using the procedure of Goering and Van Soest (1970).

Data analysis

The data from the experiments were analyzed using the GLM procedure in the ANOVA program of MINITAB (version 13.31) (Minitab 2000). Sources of variation were: diets, animals, periods, square and error in the digestibility experiment; and diets, animals, block and error in the feeding trial.

Results and discussion

Digestibility experiment

The CP content of the Mango foliage (Table 2) was low and similar to that reported by Kongmanila et al (2007). The CP in the leaves of the water spinach was lower than reported by Phathoummalangsy and Preston (2006); Phiny and Kaensombath (2006), Pheng Buntha and Ty (2006) and Samkol et al (2006).  

Contrary to the findings of Kongmanila et al (2007), there was no increase in DM intake that could be attributed to supplementation with water spinach (Table 3; Figure 1).

Figure 1. DM intake of goats fed Mango foliage alone or with rumen supplement or water spinach	Figure 2. Apparent digestibility coefficients of DM and crude protein for goats fed Mango foliage alone or with rumen supplement or water spinach

Supplementation of Mango foliage with water spinach or with the rumen supplement improved the digestibility of CP and the N retention (Table 4). However, in contrast to earlier findings in our laboratory (Kongmanila et al 2007) there was no improvement in DM apparent digestibility.

Figure 3. N balance in goats fed Mango foliage alone or with rumen supplement or water spinach	Figure 4. N retention as percentage of N digested in goats fed Mango foliage alone or with rumen supplement or water spinach

Feeding trial 

The DM intake was high increasing linearly with quantity of water spinach offered (Table 5), a response similar to that reported by Kongmanila et al (2007). DM intake of  Mango foliage was not affected by supplementation with water spinach, with the result that total DM intake increased linearly with level of supplementary water spinach, which accounted for 14, 28 and 36% of total DM intake (Figure 5).

Figure 5. DM intake of water spinach and Mango foliage in goats fed Mango foliage ad libitum and water spinach at levels of 0.5, 1.0 and 1.5% of live weight as DM

Growth rate was increased when the water spinach level was increased from 0.5 to 1% of live (from 14 to 28% of the diet DM) but then declined as the level of water spinach was increased to 1.5% of LW (36% of the diet DM) (Table 6). DM feed conversion was poorest on the diet with 36% of the DM as water spinach.

 It would appear that there is a threshold level for water spinach in diets for goats, beyond which N retention and growth rate decrease despite the high potential nutritive value of the water spinach (apparent digestibility of over 80% for DM and crude protein [Pathoummalangsy Khamparn and Preston 2006]).  Such a decline in performance was observed by  Pathoummalangsy Khamparn and Preston (2006) when goats increased their DM intake by 25% but had 50% reduction in N retention as the percentage of water spinach in the diet DM was increased from  26 to 40%.  These authors and Pheng Buntha and Chhay Ty (2006) observed a massive increase (by 5 to 6 times) in the excretion of urine (Figures 6 and 7) in goats fed high levels of water spinach and concluded that such high levels had a diuretic effect with consequent negative effects on both protein and energy metabolism.

Figure 6. Urine excretion by goats fed a range of forages as the sole diet (from Pheng Buntha and Chhay Ty 2006)	Figure 7 Output of urine in goats according to degree of supplementation with water spinach in a diet of cassava foliage (Pathoummalangsy Khamparn and Preston 2006)

Conclusion

• The supplementation of Mango foliage with water spinach, or with a mixture of urea/minerals (rumen supplement), improved the digestibility of crude protein and N retention in growing goats, but did not appear to affect DM digestibility.
  
  
• Increasing the level of water spinach as a supplement to Mango foliage from 15 to 36% (DM basis) led  to a linear increase in voluntary DM intake in growing goats.
   
• Growth rate was increased by 25% as the intake of water spinach increased from 14 to 28% in a basal diet of Mango foliage but subsequently declined to the same degree as the level of water spinach was raised from 28 to 36%.
  
  
• The poor growth performance in goats fed high levels of water spinach is attributed to the diuretic effect of this plant with a consequent negative impact on protein and energy metabolism.

References

AOAC 1990 Association of Official Analytical Chemists Official methods of analysis. 15th Edition. Arlington, Virginia. 

Chen X B and Gomes M J 1992 Estimation of microbial protein supply to sheep and cattle based on urinary excretion of purine derivatives – an overview of the technical details. An occasional publication of the Rowett Research Institute,Greenburn Road, Bucksburn, Aberdeen, AB2 95B, UK.

Chiv Phiny and Lampheuy Kaensombath 2006: Effect on feed intake and growth of depriving rabbits access to caecotrophes. Livestock Research for Rural Development. Volume 18, Article No. 34. http://www.lrrd.org/lrrd18/3/phin18034.htm

Goering H and Van Soest P 1970 Forage fiber analysis. Agricuture hand book No. 379. United States Department of Agriculture, Washington D.C, USA.

Kongmanila D, Preston T R  and Ledin I 2007 Chemical composition, digestibility and intake of some tropical foliage species used for goats, MSc Thesis, MEKARN-SLU  http://www.mekarn.org/msc2005-07/thesis07/daov2.htm

Minitab 2000 Minitab Reference Manual, Release 13.31 for Windows. Minitab Inc., USA.

Pathoummalangsy Khamparn 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, Article #35. Retrieved September 3, 2011, from http://www.cipav.org.co/lrrd/lrrd18/3/kham18035.htm

Pheng Buntha and Chhay Ty 2006: Water-extractable dry matter and neutral detergent fibre as indicators of whole tract digestibility in goats fed diets of different nutritive value. Livestock Research for Rural Development. Volume 18, Article No. 33. http://www.lrrd.org/lrrd18/3/bunt18033.htm

Pok Samkol, Preston T R and Ly J 2006: Effect of increasing offer level of water spinach (Ipomoea aquatica) on intake, growth and digestibility coefficients of rabbits. Livestock Research for Rural Development. Volume 18, Article No. 25. http://www.lrrd.org/lrrd18/2/samk18025.htm

Received 26 August 2011; Accepted 2 September 2011; Published 10 October 2011

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