Effect of mixtures of water spinach and fresh water hyacinth leaves on growth performance of pigs fed a basal diet of rice bran and cassava root meal

Ty Chhay, Khieu Borin and T R Preston^*

Center for Livestock and Agriculture Development (CelAgrid), Pras Teat village, Rolous commune, Kandal Stung district, Kandal province. PO Box 2423 Phnom Penh 3, Cambodia
chhayty@celagrid.org
^* Finca Ecológica, TOSOLY, AA #48, Socorro, Santander, Colombia

Abstract

Twenty four crossbred castrated male pigs with initial body weight from 13.7 to 15.1 kg were allocated to 6 diets containing water spinach at levels of 0, 5, 10, 15, 20 and 25% in DM, replacing fresh leaves of water hyacinth at levels of 37, 32, 27, 22, 27 and 12% in DM. The other components of the diet (DM basis) were fish meal (4-5%), soybean meal (4-5%), rice bran (26-27%) and cassava root meal (26-27%). The experiment period was 120 days. 

The replacement of 37% fresh leaves of water hyacinth by 12% water hyacinth leaves and 25% fresh water spinach (from 37 to12% of DM) with fresh water spinach (from 0 to 25% in DM) led to: (i) a 50% increase in DM intake; (ii) tripling of the rate of weight gain (from 78 to 215 g/day); and (iii) improved DM feed conversion (from 9.2 to 4.4). 

It is concluded that there are no apparent benefits from including water hyacinth leaves in diets of growing pigs.  

Key words: Growth rate, pigs, water hyacinth, water spinach

Introduction

Water hyacinth (Echhornia crassipes) floats on  water surfaces throughout SE Asia and is considered to be a common weed because of its capacity to grow and reproduce  on nutrient-rich water bodies (Le Thi Men et al 2002). Water hyacinth has been investigated since the 1979’s for the treatment of municipal water waste (Boyd 1970). The young, light-green leaves and stems are rich in crude protein (18% on a DM basis) and have been fed to pigs in the Mekong Delta (Le Thi Men 2006).

Water spinach (Ipomoea aquatica) is widely cultivated in Cambodia for human food and for feeding to pigs. Previous studies by Chhay Ty and Preston (2005) at CelAgrid showed that mixing water spinach with fresh cassava leaves (65:35 fresh basis) resulted in pig growth rates on a basal diet of broken rice, which were higher than the average recorded for diets in which water spinach or cassava leaves were fed as the sole supplement.  In a subsequent trial (Chhay Ty and Preston 2006) there were linear increases in pig growth rate when fresh water spinach replaced cassava leaves at levels of 10, 20 and 30%. 

The hypothesis that was tested in this study was that water spinach would have beneficial effects on growth rate of pigs when it replaced water hyacinth as the main source of supplementary protein in diets based on rice bran and cassava root meal. 
 

Material and methods

Location 

The experiment was carried out from 23 October 2006 to 21 February 2007 at the Center for Livestock and Agriculture Development (CelAgrid), located in Phras Teat village, Rolous Commune, Kandal stung district, Kandal province about 25km from Phnom Penh City, Cambodia. 

Experimental animals, treatments and design   

Twenty four crossbred castrated male pigs with initial body weight from 13.7 to 15.1 kg were allocated to 4 blocks according to live weight, and within blocks to 6 diets containing water spinach at levels of 0, 5, 10, 15, 20 and 25% in DM. Comparable levels of water hyacinth were: 37, 32, 27, 22, 27 and 12% in DM (Table 1). There were 4 replicates of each treatment.

The pigs were housed in individual pens with concrete floor and provided with feeders and drinking nipples. The pigs were vaccinated against common diseases in Cambodia (Swine fever and salmonellosis) and were de-wormed with Ivermectin prior to being adapted to the feeds and the housing for 10 days before starting the experiment.  

Feeds, feeding and management 

Rice bran was purchased from the rice mill near CelAgrid. Cassava root meal, fish meal and soybeans were purchased from shops in Phnom Penh city. Fresh water hyacinth leaves were harvested every day from ponds in CelAgrid or in the immediate vicinity. Water spinach was purchased from traders who harvested it from lagoons receiving waste water from Phnom Penh city. 

The water hyacinth leaves were separated from the stems and chopped into small pieces prior to being mixed with the water spinach in proportions depending on the treatments. The amounts of the feeds offered were adjusted to be close to ad libitum but with minimal residues. The mixed dry meal components of the diets were offered three times daily (8.00, 12.00 and 17.00h). After the dry meals were consumed the mixed forages were offered in amounts equivalent to the intended proportion in the diet (37% of the diet DM; Table 1).  

Data collection and analyses 

The pigs were weighed every 10 days during the 120 days of the experiment. Feeds offered and residues were recorded daily. Representative samples of feeds offered and residues were taken daily to estimate DM content, the dried samples being bulked on a weekly basis for analysis of N. The DM content was determined using the microwave method of Undersander et al (1993). N was analyzed following procedures of AOAC (1990). 

Statistical analysis 

Data for weight gain, DM feed intake, and crude protein intake and feed conversion rate were analyzed using the general linear model (GLM) option of the ANOVA software of Minitab (2000). The sources of variation were blocks, treatments and error. Relationships among variables were estimated by regression analysis using the same Minitab software. 
 

Results

Composition of diet ingredients and feed intake

The crude protein content of the water spinach was 50% higher than in the leaves of water hyacinth (Table 2).

Daily DM intake (Table 3; Figure 2) increased as the proportion of water spinach in the diet increased, but there were no differences when feed intake was expressed as a proportion of live weight.

Total intake of crude protein, and the proportion in the diet DM,  increased as water spinach replaced water hyacinth in the diet (Table 3 and Figures 1 and 3). At the highest level of water spinach, the protein from this source provided slightly more than 50% of the total diet crude protein.  

Figure 1.  Intakes of crude protein from dietary ingredients according to level of water spinach in the diet

 Growth rate and feed conversion 

Growth rate was linearly and positively related to the proportion of dietary protein derived from water spinach (Table 4; Figures 4 and 5). The relationship between DM feed conversion and proportion of dietary protein derived from water spinach appeared to be curvilinear and negative (Figure 6).