Foliage from cassava, Flemingia macrophylla and bananas
compared with grasses as forage sources for goats: effects on growth rate and intestinal nematodes

Seng Sokerya and Lylian Rodriguez

University of Tropical Agriculture Foundation, Royal University of Agriculture,
Chamcar Daung, PO Box 2423, Phnom Penh, Cambodia
kerya@uta.edu.kh

Abstract

Eight female and four male growing goats were allocated to four sources of forage which were offered as supplements to fresh brewer’s grains. The forages were:

• Fresh foliage from cassava (Manihot esculenta)
• Fresh foliage from a legume shrub (Flemingia macrophylla) (substituted occasionally by Desmanthus virgatum)
• Fresh leaves from bananas
• Natural grasses

Foliage from cassava supported the highest growth rate in the goats and the lowest faecal worm egg counts. Worm egg counts were highest in goats fed the natural grasses and the growth rates were some 30% slower compared with cassava. Very low growth rates were observed when Flemingia macrophylla and Desmanthus virgaturm foliages were fed.? Dry matter intakes of foliage were significantly less in the periods when Flemingia was fed compared with Desmanthus.

It is concluded that cassava, managed as a perennial forage, has a high potential as a protein-rich feed for goats kept in a confinement system.

Key words: Goats, growth, nematode worms, cassava, banana, Flemingia macrophylla, native grasses

Introduction

Cassava is a highly productive tropical crop that is traditionally cultivated to produce roots for human consumption or industrial extraction of starch. The leaves are a by-product from this operation and can be sun-dried prior to using them as a source of protein and vitamins in pig and poultry diets (Ravindran 1991).? Cassava can also be cultivated in a combined forage / root system with two or more harvests of the foliage prior to letting the roots develop to maturity (Wanapat et al 1997). More recently, efforts have been concentrated on managing it as a perennial forage crop with repeated harvesting at 2 to 3 month intervals (Preston et al 2000; San Thy and Preston 2001). In this system, the roots are not harvested, but serve as a nutrient reserve to support the forage re-growth.

In the Dominican Republic, Ffoulkes and Preston (1978) compared the fresh foliage of cassava with that from sweet potato, as the only source of protein and fibre in a liquid diet of molasses-urea for fattening cattle. Growth rates on the cassava foliage treatment were over 800 g day/day and were not improved when 400 g/day of additional soya bean meal was given. By contrast, growth rates on the sweet potato treatment were significantly less than on cassava and were significantly improved when soya bean meal was given. It was concluded that the cassava foliage was a better source of "bypass" protein than sweet potato foliage.? Cassava foliage has been made into “hay? in Thailand and used successfully as a source of bypass protein for dairy cattle (Wanapat et al 1997).

As is the case with most tree and shrub foliages, there are several secondary plant compounds in cassava leaves, the most widely studied being the cyanogenic glucosides (Tewe 1991). It was hypothesised that these compounds might have anthelmintic properties that could confer additional benefits on young growing goats, which are highly susceptible to intestinal nematodes.

Materials and methods

Eight female and four male goats (four females were of local breed; the rest were Bach Thao breed imported from Vietnam), with a range of initial weight from 9 to 16 kg, were allocated at random to four treatments, after blocking the animals for sex and breed type. They were housed in individual wooden pens (70 x 70cm area) on a raised slatted floor. The experiment began on 5 May and continued until 30 September, 2000.

The treatments were four sources of forage fed together with fresh brewer’s grains:

C:? ?????? Fresh foliage from cassava

FM: ???? Fresh foliage from a legume shrub (Flemingia macrophylla) (or from Desmanthus virgatum)

B: ??????? Fresh leaves from bananas

G: ??????? Natural grasses.

The forages were harvested daily from plots which had been established in the University of Tropical Agriculture (UTA) ecological farm and harvested regularly at 2-month intervals for more than one year.? The foliages from cassava, Flemingia (or Desmanthus) and the grasses were harvested after approximately 8 weeks of re-growth. The cassava and the Flemingia (or Desmanthus) were harvested by cutting the stems at about 70 cm above soil level.? The grasses were cut at 3-5 cm above soil level.? The banana leaves were harvested before they reached maturity. All the foliages were fed at approximately 10% (fresh basis) of the liveweight of the goats. The fresh brewer’s grains were received every two weeks from the brewery and were immediately ensiled in closed concrete containers. The ensiled grains were fed ad libitum.

Measurements

The goats were weighed at 14-day intervals and growth rates calculated from the linear regression of liveweight on time. Feed offered and refused was recorded daily. Samples of faeces were taken directly from the rectum starting on 21 August, 2000, and on 3 further occasions (4 September, 18 September and 2 October). Samples of faeces (4 g) were ground and mixed with 56 ml of flotation fluid (either 1250 g sugar and 1 litre water or 450 g salt and 1 litre water). After filtering through a “tea strainer?, a sub-sample was transferred to both sides of a McMaster counting chamber and allowed to stand for 5 minutes. All eggs and coccidian oocytes were counted under a microscope at 10x10 magnification.

The growth, feed intake and faecal egg count data were analysed by the GLM option of the ANOVA software from Minitab (version 12.1). Variables were diet and error.? Data for faecal egg counts were transformed using the Box-Cox option in the Minitab software.

Results and discussion

Goats fed cassava foliage grew faster (P=0.01) than those fed the other forages (Table 1; Figure 1).

Those fed grass had better growth rates than those fed banana leaves while those fed leguminous foliages grew slowest of all. Total daily dry matter intake was highest on cassava and lowest for the grass treatment (P=0.001).? Forage dry matter intake was lowest when grass was fed and highest for cassava.? The opposite occurred with intake of spent grains, which were 33% greater on grass than on cassava.? Thus cassava accounted for almost 60% of the total dry matter intake compared with 31% for the grass treatment. The feed conversion data, as expected, followed the trends in liveweight gain.

In a previous trial with growing Bach Thao goats (initial weight 11 kg) in UTA, Mon Thy (1999) reported a similar order of difference between those fed cassava foliage or native grass as forage supplements for spent brewer’s grains, although overall growth rates were higher (77ƒA6.1 and 49ƒA4.7 g/day, for cassava and grass, respectively).

Flemingia was fed on days: 1-19, 44-84 and 102-126 and Desmanthus on days 20-43, 85-101 and 127-140.? A comparison of dry matter intakes when these legume forages were fed shows marked differences in palatability (Table 2) with DM intakes of Flemingia being only half what was recorded with Desmanthus.? Surprisingly, when the goats had low intakes of Flemingia they did not compensate by eating more spent grains, thus total dry matter intake was much less when Flemingia was fed. The low acceptance rate by goats of Flemingia macrophylla ?was reported in Vietnam by Nguyen Thi Mui (2000, personal communication).

?

Figure 1: Growth rates of goats fed foliages of Flemingia macrophylla / Desmanthus virgatum
(FM-DV), banana, grass and cassava as supplements to brewer’s spent grains

The number of Trichostrongyle eggs in faecal samples was low on all forage treatments on the first two sampling dates (after 109 and 123 days from starting the trial) but increased markedly in the 3^rd and 4^th samples (after 137 and 151 days, respectively), with extremely high values reported on the grass treatment (Table 3 and Figure 2). The values for the cassava treatment were indicative of only a “light" infestation, while those for goats fed the grass were indicative of a “heavy? infestation which would warrant treatment with an anthelmintic.

Figure 2: Worm egg counts (Trichostrongyle spp.) in growing
goats fed different forages as a supplement to fresh brewer’s grains
(numbers refer to sampling dates which were: 1= 21August;
2=4 September; 3=18 September; 4=02 October)

Two possibilities exist to explain the apparently lower nematode worm burden in goats fed the tree / shrub foliages compared with the grass.? One is that the foliages were a poorer host for the infective larvae; the other is that the non-nutritional compounds present in the foliages possess a degree of anthelmintic activity against nematode worms.? From the standpoint of the farmer, with limited land area, cassava offers other advantages.? It is highly productive (San Thy and Preston 2001) with annual yields of over 100 tonnes/ha of fresh foliage when fertilized with goat manure or biodigester effluent; and it is easily harvested, in terms of quantity of biomass that can be cut and collected per unit of time.

Conclusions

Foliage from cassava managed as a perennial shrub supported the highest growth rate in the goats and the lowest faecal worm egg counts. These findings, when considered along with the agronomic data showing high yields of biomass without use of agrochemicals, indicate a very high potential of cassava to contribute to sustainable agriculture in Cambodia and other tropical countries.

Acknowledgements

We acknowledge financial support from the regional project “Development and Testing of an Integrated Approach to the Control of Gastro-Intestinal Parasites of Small Ruminants in South and South East Asia (TAG 433)" in setting up our field laboratory. The advice and practical guidance on culturing larvae and worm egg counting, received from the project coordinator Dr Doug Gray, was highly appreciated.

References

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Mon Thy 1999? Cassava foliage compared with grass as a supplement for goats given brewer’s spent grains as the basal diet.? BSc Thesis. Royal University of Agriculture, Phnom Penh, Cambodia

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