Effect of different ratios of water spinach and fresh cassava leaves on growth of pigs fed basal diets of broken rice or mixture of rice bran and cassava root meal

Chhay Ty and T R Preston^*

Centre for Livestock and Agriculture Development (CelAgrid-UTA Cambodia)
PO box 2423, Phnom Penh, Cambodia
chhayty@utafoundation.org
^*Finca Ecológica, TOSOLY, UTA (Colombia)
AA #48, Socorro, Santander, Colombia
trpreston@mekarn.org

The original version of this paper was published in Livestock Research for Rural Development (http://www.cipav.org.co/lrrd/lrrd18/4/chha18057.htm)

 

Abstract

Twenty four crossbred (Local*Landrace or Local*Duroc) castrated male pigs weighing from 16.0 to 18.4 kg were used in a 2*3 factorial arrangement to study the effect of (i) different levels of substitution of wilted cassava leaves by water spinach; and (ii) a basal diet of broken rice or a mixture (50:50) of rice bran and cassava root meal. The feeding trial lasted for 120 days from 8 August to 6 December 2005.

Higher intakes of water spinach and cassava leaves, and of total DM,  were observed when the basal diet was broken rice rather than rice bran mixed with cassava root meal. Increasing the replacement of cassava leaves by water spinach from 10 to 30% resulted in increases in intake of the energy component, in the total quantity of foliage, and of total DM. Growth rates tended to be higher on the  broken rice diet than on rice bran and cassava root meal; while the 30% level of water spinach was superior to the 10% level.

The overall trend of live weight gain as a function of level of water spinach was curvilinear and positive, indicating a synergistic effect on performance from mixing increasing amounts of water spinach with fresh cassava leaves.

Key words: cassava leaves, growth, broken rice, cassava root meal, rice bran, pigs, protein, water spinach

Introduction

In a previous experiment (Chhay Ty and Preston 2005) with growing pigs fed a basal diet of broken rice, we showed that a supplement of a 50:50 mixture (DM basis) of water spinach (Ipomoea aquatica) and fresh cassava leaves supported growth rates that were 32% higher than the average of the growth rates on the two sources of foliages fed separately. In the present experiment the hypothesis to be tested was that lower proportions of water spinach would also have a synergistic effect on growth of pigs fed low protein basal diets.

Materials and methods

Location

The experiment was carried out from 8 August to 6 December 2005 in the Center for Livestock and Agriculture Development (CelAgrid-UTA Cambodia), located in Kandal village, Rolous Commune, Kandal Steung district, Kandal province, about 25km from Phnom Penh City, Cambodia .

Experimental animals, treatments and design

Twenty four crossbred (Local*Landrace or Local*Duroc) castrated male pigs with initial body weight from 16 to 18.4 kg were allocated to six treatments with 4 replicates per treatment in a 2*3 factorial arrangement. The factors were:

Energy

• Broken rice

• Cassava root meal mixed with rice bran

Protein supplement

Proportions of water spinach (WS) and fresh cassava leaves (FCL) in ratios (DM basis) of:

• WS 10% and FCL 90%

• WS 20% and FCL 80%

• WS 30% and FCL 70%

The pigs were allocated into 2 blocks according to live weight (means for each block were 14.6 and 20.3 kg). The nutritional treatments were applied at random within each block. The pigs were housed in individual pens with concrete floors and provided with feeders and drinking nipples. The pigs were vaccinated against Salmonella disease and were adapted to the feeds and the housing for 7 days before starting the experiment.

Feeding and management

Broken rice and rice bran are by-products of Cambodian rice mills and were available in the local area. Cassava root meal was purchased from a store in the city. Fresh cassava leaves were harvested every day from plots in CelAgrid (Photo 1) or they were purchased from a farmer near the center. The water spinach was purchased from traders who harvested it from lagoons receiving waste water from Phnom Penh city.

The leaves plus stems of the water spinach and the leaves of cassava (after removing stems and petioles) were chopped into small pieces and wilted over-night and then mixed with the other ingredients of the diet (Tables 1 and 2) before being offered in 3 meals at 8.00, 12.00 and 17.00h. The amounts of feeds offered were based on the allowance of 40 g DM per 1 kg live weight of the pigs, with the broken rice (or mixture of rice bran and cassava root meal) supplying 50% and  the mixtures of leaves providing the remainder. 

 

Data collection and analyses

The pigs were weighed every 10 days during the trial which lasted 120 days. Individual feeds offered and residues were recorded daily. Samples of feeds and residues were analysed for DM, N and HCN. The DM content was determined using the micro-wave method of Undersander et al (1993). N and HCN were determined following procedures of AOAC (1990).

Statistical analysis

Data for weight gain, DM feed intake, crude protein intake, HCN intake and feed conversion rate were analysed using the general linear model (GLM) option of the ANOVA software of Minitab (2000). The sources of variation were blocks, level of water spinach, energy, interaction energy*level of water spinach and error.

Results and discussion

Feed intake

Higher intakes of water spinach and cassava leaves were observed when the basal diet was broken rice rather than rice bran mixed with cassava root meal (Table 3), with total DM intakes being higher for the former when expressed on a live weight basis. Replacing cassava leaves with water spinach resulted in increases in intake of the energy component, and in the total quantity of foliage, but a decrease in the intake of cassava leaves (Figures 1 and 2).

 

Figure 1: Relative intakes of diet ingredients according to degree of
substitution of cassava leaves by water spinach

On a live weight basis the HCN levels consumed were 4.99, 4.1 and 2.86 mg/kg LW, for the water spinach 10, 20 and 30% levels, respectively. These were lower than in the earlier study (Chhayty et al 2005) and in the range reported as potentially toxic: 1.4 by Getter and Baine (1938), 2.1 to 2.3 by Johnson and Ramond (1965), 3.5 by Tewe (1992) and 4.4% of LW by Butler (1973).

Growth and feed conversion

Growth rates tended to be higher on the  broken rice diet than on rice bran and cassava root meal during the initial,  final and overall  trial period. For the periods 40 to 80, 80 to 120 and overall, the 30% level of water spinach was superior to the 10% level.

Table 4: Mean values for initial and final live weights, and growth rates, of pigs fed broken rice or a mixture of rice bran and cassava root meal supplemented with different levels of water spinach replacing fresh cassava leaves
	Energy				Water spinach, % replacement of cassava leaves
Days	BR	RBCRM	SEM	Prob.	WS10	WS20	WS30	SEM	Prob.
Growth rate, g/day
0-40	273	225	16.9	0.07	234	229	284	20.8	0.15
40-80	327	293	19.3	0.24	249a	321ab	360b	23.8	0.013
80-120	427	341	18.5	0.06	3394a	355a	456b	22.6	0.004
0-120	337	290	17.5	0.079	267a	306ab	367b	21.4	0.015
Live weight, kg
Initial	17.7	17.3	0.69	0.67	18.0	16.0	18.4	0.84	0.13
Fina1#	58.2	50.2	2.3	0.025	49.7a	52.6a	60.4b	2.9	0.044
ab Means  within rows without common letter are different at P<0.05 # Adjusted for differences in initial weight

 

Figure 2: Growth curves of pigs fed basal diet of  broken rice supplemented with different levels of water spinach (WS) replacing cassava leaves		Figure 3: Growth curves of pigs fed basal diet of rice bran and cassava root meal supplemented with different levels of water spinach (WS)  replacing cassava leaves

Figure 4: Growth rates of the pigs during successive 40 day periods and overall, according to supplementary level of water spinach with  basal diet of broken rice		Figure 5: Growth rates of the pigs during successive 40 day periods and overall, according to supplementary level of water spinach with  basal diet of rice bran and cassava root meal

The overall trend of live weight gain as a function of level of water spinach was curvilinear and positive (Figures 6 and 7), indicating that the rate of increase in live weight gain by replacing cassava leaves with water spinach was more marked the higher the level of water spinach in the diet. The growth curves in Figures 2 and 3 indicate a similar trend.

Figure 6: Relationship between growth rate and  replacement of cassava leaves  by water spinach on broken rice diet		Figure 7: Relationship between growth rate and  replacement of cassava leaves  by water spinach on diet of rice bran and cassava root meal

Feed conversion was better on the basal diet of broken rice than on the mixture of rice bran and cassava root meal and tended to improve (P=0.12 for the overall trial period) with increasing levels of water spinach (Table 5).

Table 5: Mean values for DM feed conversion of pigs fed broken rice or a mixture of rice bran and cassava root meal supplemented with different levels of water spinach replacing fresh cassava leaves
	Energy				Level of water spinach
Days	BR	RBCRM	SEM	Prob.	WS10	WS20	WS30	SEM	Prob.
0-120	3.44	4.06	0.07	0.001	3.91	3.70	3.65	0.08	0.12
ab Means  within main effects within rows without common letter are different at P<0.05

Conclusions

• The synergistic effect on growth rate of pigs of replacing cassava leaves with water spinach, as the main protein source, was confirmed in that the relative response to substituting cassava leaves with water spinach increased as the degree of replacement was increased.

• There were no indications of HCN toxicity on any of the diets
   

Acknowledgments

The authors would like to express their gratitude to the MEKARN project financed by the SIDA-SAREC Agency, and to the Center for Livestock and Agriculture Development (CelAgrid UTA-Cambodia), for providing resources for conducting this experiment

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