Effect of feeding processed cassava foliage on growth performance and nematode parasite infestation of local goats in Laos

Vanthong Phengvichith and T R Preston*

Research Management Division, National Agriculture and Forestry Research Institute,
Ministry of Agriculture and Forestry, P. O. Box 811, Vientiane, Lao PDR.
vanthong.p@nafri.org.la
* Finca Ecológica, TOSOLY, AA #48, Socorro, Santander, Colombia

Abstract

Thirty goats  were grazed during the day on native pasture and then (at 5.00pm) housed in individual pens where they were allocated to five supplement treatments: No supplement, Guinea grass, wilted cassava foliage, ensiled cassava foliage or sun-dried cassava foliage.  

Feeding cassava foliage (wilted, sun-dried or ensiled) increased growth rates and reduced nematode parasite egg counts (EPG) compared with un-supplemented goats. Feeding of Guinea grass improved growth only slightly and had no effect on EPG.

Keywords: EPG, grazing, Guinea grass, silage, sun-drying, wilting

Introduction

Productivity of small ruminants, especially goats, in many tropical areas is often poor and has been related to limitations caused by parasites,  inadequate nutrition, unimproved genotypes and poor management (Devendra and Burns 1983). Goat production in Laos is to almost 100% found in small-holder farms integrated with crop production in low input and low output production systems. The goat is commonly in a free range system, and relies mainly on grazing native grass and forages which often have low nutritive value. The animals are given little or no energy and protein supplements.

Parasitic nematodes of the digestive tract remain one of the main constraints to small ruminant production both in temperate and tropical countries (Woolaston and Barker 1996; Hoste et al 2005). The usual mode of control of these gastrointestinal nematodes based on repeated use of anthelmintics is now strongly questioned because of the increasing development of resistance to chemical medicines (Waller 2005). The manipulation of host nutrition in order to improve the host resistance and/or resilience to parasite infections seems to represent one of the most promising options (Hoste et al 2005). Goats which are well nourished will grow and reproduce faster and are better able to withstand the effects of worm infection than those given a low plane of nutrition (Peacock 1996).

Previous studies showed that feeding cassava foliage hay to penned goats resulted in improved growth performance (Ngo Tien Dung et al 2005; Phengvichith and Ledin, 2006). Apart from the nutritional benefit that has been obtained in ruminants fed on cassava foliages containing a moderate concentration of tannins (CT), a reduction in the number of parasite eggs in the faeces has been also observed (Netpana et al 2001; Seng Sokerya and Preston 2003; Ngo Tien Dung et al 2005). The effect of of cassava foliage supplementation in free grazing goats has not been extensively studied.

The aims of the present study were to investigate the effect of different methods of processing cassava foliage on the growth performance and parasite infestation of local goats managed in the traditional grazing system.
 

Materials and methods

Location and climate of the study area 

The experiment was conducted in the Northern Agriculture and Forestry Research Centre, Luang Prabang Province, which is located about 40 km from Luang Prabang Town to the South-west, at an altitude of 300 m above sea level. The climate in this area is tropical monsoon, with a wet season from May to October and a dry season from November to April. Annual rainfall averages about 1600 mm and the peak occurs in the period July to August. The temperatures and relative humidity ranges during the study were 22-28^oC and 70-90%, respectively. The experiment was carried out for 90 days from the end of the wet season to the beginning of the dry season (August to November, 2008).

Experimental design

Grazing goats were assigned in a completely randomized block design to five treatments consisting of different forms of supplementation in overnight confinement after day-time grazing:

• NS: No supplement
• GG: Guinea grass
• WCF: Wilted cassava foliage
• SDCF: Sun-dried cassava foliage
• ECF: Ensiled cassava foliage

Preparation of the experimental feeds

The Guinea grass was obtained from existing pastures near the experimental unit. About 0.5 ha of the pasture was divided into 5 plots, which were mechanically cut at the beginning of the wet season before the start of the experiment. Nitrogen fertilizer (urea) was applied initially at the rate of 100 kg of urea/ha, and subsequently after each cutting at 45 day intervals with an amount of 50 kg of urea/ha at each occasion. The forage was manually harvested about 25 to 30 cm from the ground every afternoon at 14:30 h. Before feeding, the fresh grass was chopped into 30 to 40 cm pieces.

The cassava foliage was obtained from an area of about 0.5 ha which had been planted in the early growing season (April 2008). Three months after planting, the foliage was harvested for making hay and silage. The aerial parts, 40 to 50 cm from the top including leaves, petioles and young stems, were collected, and mechanically chopped into 5-7 cm pieces. One part was laid in the sun during 2 to 3 days, depending on the intensity of sun light, with the aim of reducing the moisture content to less than 12%. The sun-dried foliage was then stored in bags until needed.  For the silage treatment, the rest of the foliage after chopping was mixed with 10% of rice bran (fresh weight basis), and stored in sealed plastic bags for at least three weeks before feeding. For the wilted cassava treatment, the foliage was harvested every morning (about 9:00 h) and was wilted for about 7 hours before feeding.

Experimental animal and management

Thirty local goats (15 males and 15 females) were purchased from farmers in the villages around the research station. They were approximately 5 months old and weighed 14.0±0.5 kg. They were allowed to graze freely during the day in the native pasture around the experimental station and until at 17.00h they were housed in individual pens (1.5 m x 0.80 m), in an open-sided house with corrugated aluminium sheet roofing and concrete floor. The supplements were offered individually after the goats were confined until the following morning. Feeding was ad libitum in the amount of 120% of the average daily consumption of grass or processed cassava foliage in the previous week.  

A mineral salt-lick block (Ca 145 g, Cl 375 g, Na 242 g, Fe 320 mg, Cu 295 mg, Mn 185 mg, Co 80 mg, Zn 280 mg, Se 20 mg, I 300 mg and Mg 2400 mg per kg block) and water were supplied to each goat on all the treatments.  Feed troughs were used for the ensiled cassava foliage, the cassava hay and the Guinea grass. For those animals in the treatment with wilted cassava foliage, this was hung on the wall of each individual pen. All animals were vaccinated against Haemorrhagic septicaemia and adapted to the feeds and pens during 14 days before starting the experiment.

Measurements

The goats were weighed when the experiment started and then once per week always at the same time at 7:00 h in the morning before they were released for grazing. Feed offered and refused was  recorded individually in the morning. Dry matter (DM) content of the feeds offered and refused was determined daily using a microwave oven (Undersander et al 1993).  Samples of offered feeds and refusals were taken daily and pooled weekly, with two sub-samples being taken for chemical analysis.

The weekly pooled samples were analysed for DM, nitrogen (N) and ash. N and ash were analyzed according to standard methods (AOAC 1990). Analyses of neutral detergent fibre (NDF) and acid detergent fibre (ADF) were done following the procedures of Van Soest et al (1991). Crude protein (CP) was calculated as N*6.25.

Samples of faeces were collected from all animals at the start of the experiment to check the level of parasite infestation. New samples were taken for all animals at 30 days, 60 days and 90 days of the experimental period. Samples were taken to the provincial veterinary laboratory in Luang Prabang for determining species of parasites, using a modified Wisconsin sugar floatation technique as described by Jordan et al (1988) and the EPG according to the procedure of Hansen and Perry (1994). To determine EPG, about 4 g of faecal sample were ground and mixed with 56 ml of flotation fluid (a saturated sugar solution in water). After filtering through a “tea strainer”, a sub-sample was transferred to both compartments of a McMaster counting chamber and allowed to stand for 5 minutes. All parasite eggs were counted under a microscope at 10x10 magnifications and multiplied by 50 to yield the EPG of faeces.

Statistical analysis

Data were analyzed using the General Linear Model in the ANOVA program of the Minitab (2000) software.  Treatment means showing significant differences at the probability level of P<0.05 were compared using Tukey’s pairwise comparison procedure. The statistical model included diet effect, block effect, and where appropriate, covariance was us\ed to correct comparisons to the same initial weight. All means, unless otherwise stated, are least squares means. The following model was used:

Y_ij = μ + T_i + B_j +  βX_ij + e_ij

Y_ij : the dependent variable; μ : general mean; T_i : effect of diet; B_j: effect of block; βX_ij : effect of initial weight as a covariate; e_{ij :}  experimental error. Before analysis, EPG was subjected to logarithmic transformation (log₁₀ x + 1) to approximate normal distribution.

Results and discussion

 Feeds and feed intake

 NDF and ADF concentrations were higher, and CP lower, in Guinea grass than in the cassava foliages (Table 1).

 DM intake of the supplements was similar on all treatments; however CP intake was twice as high on the cassava foliages with no differences among the different forms of processing (Table 2).

Live weight gain

Daily live weight gains were almost twice as high in goats fed cassava foliages compared with the un-supplemented controls. Growth  rate with a supplement of Guinea grass was better than on the control diet but lower than for the cassava foliages (Table 3; Figure 1).These results are in agreement with those of Ho Quang Do et al (2002), Seng Sokerya and Preston (2003) and Ho Bunyeth and Preston (2006) where the goats supplemented with cassava foliage had faster growth and better feed conversion rate than goats given grass or grazing only.  There were no differences in growth rate among the different ways of processing the cassava foliage and no indications of toxicity due to HCN, even on the foliage wilted for 7 hours which on the basis of other reports (Du Thanh Hang and Preston 2005) would have only lowered the HCN to 932 mg/kg DM whereas on sun-dried and ensiled cassaa foliage, HCN levels were recorded as 215 and 120 mg/kg DM, respectively (Ho Bunyeth and Preston 2006).

Figure 1. Mean values of growth rate of goats given different supplements at night-time after day-time grazing

Parasite infestation 

Most of parasite species were found to be  Haemonchus contortus and Strongylus spp.   The EPG counts were similar for all treatments at the starting point (Table 4). On the un-supplemented control and  Guinea grass treatments, the parasite infection increased almost linearly over time reaching values after 90 days close to 10 thousand EPG (Figure 2). On the cassava treatments, the EPG counts increased slightly over time but to a much lesser extent than on the control or Guinea grass treatments. A reduction in nematode infestation in goats supplemented with fresh cassava foliage, compared with goats fed grass, as evidenced by lower EPG values in feces, was first reported by Seng Sokerya and Rodriguez (2001) and Seng Sokerya and Preston (2003). In more detailed studies (Seng Sokerya et al 2009) it was shown that goats fed both fresh and ensiled cassava foliage had reduced worm fecundity (reduced EPG) while in those fed the ensiled foliage (but not the fresh foliage) there was also a decreased worm burden. Beneficial effects of the improved protein  status on the health of the goats fed cassava foliage could also be expected as it has been shown that protein supplementation of infected sheep or goats helped them to mount an effective immunological response to the infection (Horste et al 2005). However, in further work by Seng Sokerya et al (2010), the improvement in protein nutrition by feeding soybean meal, although effective in improving growth and reducing anaemia, had no effect on the worm burden or worm fecundity. 

Table 4. Mean values for parasite egg count of the goats supplemented with different forages or none
	No supplement	GG	WCF	CHF	ESCF	SEM
Days	Eggs per g feces, EPG
0	1442	1692	1475	1467	1717	119
30	3300a	3358a	2825a	3042a	2483b	174
60	3958a	4092a	2942b	2767c	2742c	220.6
90	9750a	9742a	3933b	3975b	3000b	547
a bc Means within rows without common superscript differ at P<0.05

Figure 2. Worm fecundity (EPG) in goats grazed during the day and given forage supplements at night-time

Conclusions

• Feeding cassava foliage (wilted, sun-dried or ensiled) to goats housed at night after day-time grazing increased growth rates and reduced nematode parasite egg counts (EPG).

• Supplementation with Guinea grass improved growth only slightly and did not reduce the EPG.

Acknowledgements

The authors gratefully acknowledge the support for this research provided by the MEKARN program, funded by the Swedish International Development Agency, Department for Research Cooperation (Sida/SAREC). Appreciation is also expressed to the staff of the Northern Agriculture and Forestry Research Centre for help in the field operations, and the Veterinary Laboratory at Luang Prabang for parasite egg count analysis and animal health service.
 

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Received 15 November 2010; Accepted 21 December 2010; Published 5 January 2011

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