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

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

Livestock Research Center, Namxuang, Lao PDR,
^*Center for Livestock and Agriculture Development (CelAgrid)
chhayty@celagrid.org
^**UTA-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 (10, 20, 30 and 40%)  in a basal diet of cassava root meal and rice bran on feed intake, digestibility and N balance.  Apparent digestibility of DM and crude protein, daily N retention and N retention as percentage of N digested, werfe improved as the level of water spinach was increased to 40% of the diet DM

Key words: crude protein, Mong Cai crosses, Laos
 

Introduction

Pig production plays an important role in the farming activities especially for smallholder farmers in Lao DPR. The pigs provide manure, meat and income. In recent years, the income from pig raising has decreased and in some cases has been negative because the pigs grow slowly. The main cause is the lack of protein to enhance the available energy sources such as rice bran and cassava root by-products. These feeds have a low protein content that do not meet the requirement for growing pigs. Therefore, there is a need to identify and promote other protein sources especially those that can be produced on the farm such as water spinach, cassava leaves and other protein-rich foliages.

In recent studies by Chhay Ty et al (2005a,b,c) it was shown that water spinach can be a major source of supplementary protein in diets based on broken rice or rice bran mixed with cassava root meal for growing pigs. The feeding of water spinach improved feed intake, growth rate and feed conversion, and increased the digestibility of DM, organic matter, crude protein and crude fibre.

This study was focused on the effect of different levels of water spinach on intake, apparent digestibility and nitrogen balance in growing pigs fed a basal diet of cassava root meal and rice bran.

 

Materials and methods

Location and duration

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

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 (Table 1).

Animals and housing

Four crossbred (Mong Cai*Large White) castrated male pigs with live weight from 8.0 to 10.0 kg were used in the experiment. They were housed in wooden metabolism cages that allowed 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.

Feeds and feeding system

The diets were formulated so that the crude protein content increased in line with the rate of substitution of the rice bran by the cassava root meal so that the expected increase in digestible energy from the cassava root would be balanced by more protein from the water spinach (Table 2).

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

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 was 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

The rice bran was low in crude protein probably because of contamination with a part of the husks.

Feed intake

Total voluntary feed intake was higher on the diets with 10 and 20% water spinach compared with the higher levels (Table 4; Figure 1)..

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

The dry matter content of the faeces decreased as the level of water spinach increased (Table 5).

Apparent digestibility

Dry matter and crude protein apparent digestibility increased with increasing level of water spinach (Table 6 and Figure 2).

Nitrogen retention

Daily N retention increased with the level of water spinach (Table 7) in the diet. There were very close relationships between the level of water spinach and N retained daily and N retained as percentage of N digested (Figures 3 and 4).

The improvement in diet digestibility and N retention as water spinach and cassava root meal replaced rice bran is to be expected as both these feeds have less fibre than the rice bran that was replaced. It is equally apparent that the biological value of the protein in water spinach is superior to that in rice bran. The beneficial effects of including water spinach in pig diets based on rice byproducts have been reported in several recent studies (Chhay Ty et al 2005a,b,c).

Conclusions

Nutrient digestibility and N balance were improved when water spinach and cassava root meal replaced rice bran in diets of young growing pigs. 

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.

Bounhong Norachack, Soukanh Keonouchanh, Chhay Ty, Bounthong Bouahom and Preston T R 2004: Stylosanthes and cassava leaves as protein supplements to a basal diet of broken rice for local pigs. Livestock Research for Rural Development. Vol. 16, Art. No. 74. http://www.cipav.org.co/lrrd/lrrd16/10/boun16074.htm

Chhay Ty and Preston T R 2005a Effect of water spinach and fresh cassava leaves on intake, digestibility and N retention in growing pigs. Livestock Research for Rural Development. Vol. 17, Art. #23. Retrieved June 30, 2005, from http://www.cipav.org.co/lrrd/lrrd17/2/chha17023.htm

Chhayty, Preston T R 2005b Effect of water spinach and fresh cassava leaves on growth performance

of pigs fed a basal diet of broken rice Livestock Research for Rural Development 17 (7) 2005, from http://www.cipav.org.co/lrrd/lrrd17/7/chha177.htm

Chhay Ty, Preston T R 2005c Effect of fresh water spinach and fresh cassava leaves or as a mixture

on intake, digestibility and N retention in growth pigs. Livestock Research for Rural Development

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

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