Effect of different levels of water spinach inclusion in a basal diet of cassava root meal and rice bran on intake, nutrient digestibility and nitrogen balance in growing pigs

Bounhong Norachack, Soukanh Keonouchanh, T R Preston* and Chhay Ty^**

Livestock Research Center, Namxuang, Lao PDR,
^*University of Tropical Agriculture, Cambodia
chhayty@celagrid.org

**UTA-TOSOLY - Finca Ecológica, Socorro, Colombia

Abstract

 Four crossbred (Mong Cai*Large White) castrated male pigs of 8.0 to 10.0 kg were used to study the effect of different levels of water spinach inclusion (10, 20, 30 and 40%)  in a basal diet of cassava root meal and rice bran on the intake, nutrient digestibility and N balance. Total dry matter (DM) intake and feed intake as percentage of body weight decreased with increasing levels of water spinach (P<0.001) and nutrient digestibility and N balance increased with increasing levels of water spinach in the diet.
 

It was concluded that nutrient digestibility and N balance were improved when water spinach was included at levels of up to 40% in diets of growing pigs.

Key words: digestibility, growing pig, nitrogen balance, water spinach,
 

Introduction

Materials and methods

Location and duration

The experiment was conducted at the Livestock Research Center of the National Agriculture and Forestry Institute (NAFRI), Namxuang, about 44 km from Vientiane City, Lao PDR, from 28 February to 7 April 2005.

Treatments and design

There were four treatments:

·                     WS10: Water spinach 10% and rice bran 90%

·                     WS20: Water spinach 20%, rice bran 70% and cassava root  meal 10%

·                     WS30: Water spinach 30%, rice bran 50% and cassava root  meal 20%

·                     WS40: Water spinach 40%, rice bran 30% cassava root  meal 30%

The experimental design was a Latin square 4*4 arrangement with 4 pigs and 4 periods.

Animals and housing

Four crossbred (Mong Cai*Large White) castrate pigs with live weight from 8.0 to 10.0 kg were used in the experiment. The pigs were housed in wooden metabolism cages that allow the separate collection of urine and faeces (Photo1). The size of the metabolism cages was 0.8m x 0.8m (Bounghong et al 2004). The experimental periods were each of 12 days: 7 days for adaptation to allow the pigs to become familiarized with the new diet and a five-day period for collection of faeces and urine.

Photo 1: Metabolism cage made from wood for digestibility and N retention studies

Feeds and feeding system

The pigs were fed the diets shown in table 2. The cassava roots were harvested from plots at the Livestock Research Center, and after harvesting were chopped by machine (Picture 2) and dried for 3-4 days until completely dry. Water spinach was purchased in the first 2 months and then later on was harvested in the center. Rice bran was purchased from a rice mill near the center.

Measurements

Urine and faeces of each pig were collected separately and weighed daily every morning and stored at -20 ⁰C. Urine was collected in a bucket via a plastic sheet and funnel placed below the cage. To prevent nitrogen losses by evaporation of ammonia, the pH was kept below pH 4 by putting 10ml of 10% sulphuric acid in the urine. The urine and faeces from each animal were collected for five days and at the end of the period the faeces were mixed, ground and representative samples taken for analysis. Dry matter of feed offered, refused and faeces was done by microwave radiation (Undersander et al 1993). Nitrogen in faeces, urine, feeds offered and refused were determined according to the Kjeldahl method (AOAC 1990).

Statistical analysis

The data were analysed using the GLM option of the Minitab (version 13.31) ANOVA software. Sources of variation were feed, periods, pigs and error.

Results and discussion

Feed characteristics

Feed intake

The diets with 10 and 20% water spinach were completely consumed. Total voluntary feed intake decreased with increasing level of water spinach (Table 4). The dry matter intake as percent of body weight was highest for WS20, followed by WS10.

Figure 1: Daily intake of dry matter, water spinach, cassava root meal and rice bran

Faecal characteristics in pigs fed water spinach, cassava root meal and rice bran

The dry matter content of the faeces decreased when the pigs were the diets with high levels of water spinach (Table 5).

Digestibility coefficients

Dry matter and N digestibility increased with increasing level of water spinach  (Table 6 and figure 2).

Figure 2: Dry matter and Nitrogen digestibility (%) of diets containing different levels of water spinach, cassava root meal and rice bran

Nitrogen retention

Daily N retention increased with level of water spinach (Table 7) in the diet and there was a very close relationship between the level of water spinach and N retention (Figure 3).

Figure 3: N retention increases with levels of water spinach

Conclusions

Nutrient digestibility and N balance were improved when the level of water spinach in diets of pigs was increased. 

Acknowledgements

The authors would like to thank SIDA-SAREC for funding this experiment through the MEKARN regional project, and staff of the Livestock Research Center, NAFRI, for their cooperation.

 

References

AOAC 1990: Official methods of analysis. Association of Official Analytical Chemists, Arlington, Virginia, 15^th edition, 1298 pp.

Undersander D, Mertens D R and Theix N 1993: Forage analysis procedures. National Forage Testing Association. Omaha pp 154.