Effects of fresh or sun-dried cassava foliage on growth performance of goats fed basal diets of Gamba grass or sugar cane stalk

Bounthavone Kounnavongsa, Vanthong Phengvichith* and T R Preston**

Livestock Research Center, National Agriculture and Forestry Research Institute

kounnavongsa@gmail.com, kounnavongsa@yahoo.com

*National Agriculture and Forestry Research Institute

 Ministry of Agriculture and Forestry, P.O. Box 811, Vientiane Laos

**Finca Ecológica,UTA-Colombia, AA#48, Socorro, Santander, Colombia

Livestock production systems in Laos

Agriculture is the mainstay of the economy in Laos. For the rural smallholders, who contribute most of the country’s agricultural output, livestock keeping is often a vital source of cash income, a means to accumulate assets, and a provider of inputs to crop production.  Cattle, buffaloes, pigs, chickens and goats are the most important livestock species in the country (Table 1).

Demand for meat is increasing, and there is growing potential for exporting livestock and their products to neighboring countries. There is great potential to enable a dynamic development of the livestock and fisheries sub-sector. Relatively extensive land areas throughout the country are well suited to pasture and fodder production. An estimated 7 to 8 million hectares of grazing land and associated water resources are underutilized; comprising natural grasslands, forests, barren lands, inland water resources, and reservoirs of which about two thirds are located in the uplands. It is estimated that in the future ruminant production in upland areas will increase and supply the demand of the lowland and urban area, as intensification and mechanization in the lowland decreases land availability for grazing goats.

Livestock in Laos offer today one of the most promising opportunities for Lao farmers and foreign investors to commercialize with high value products. According to the economic growth in the region, domestic and regional demand for livestock products is expected to increased.

Market demand for local consumption and export of goat meat is strong, the price per kg of live weight presently being about US$1.7 to 2.0 and more expensive than cattle and buffalo meat which sells at  US$1.3 to 1.5 per kg. Recently, according to data surveyed, the price of live goat trade in Savannakhet province in June 2009 has increased up to US$ 2.7 per kg live animal. This is one reason for the relatively high rate of increase in the goat population over the last 20 years (Stür et al., 2002). The government has adopted a livestock development plan to strengthen and promote animal production and enhance national food security.

Farmers raise animals predominantly by traditional methods based on low input and low output production systems so the output per animal is not high. The animals are mainly indigenous and kept mostly under free range conditions; they feed themselves by grazing the natural grassland, in paddy fields after the harvest, on fallow land, in the communal land, and in the forest. The free range system means that there is often no selection of breeding animals. There is lack of information about livestock breeds; only pigs have been described (Table 2).

Feed resources are inadequate, and diseases and parasites are the main constraints on livestock production. The animal production systems are recently changing in the lowland area, particularly in the irrigated rice production area, where instead of one rain-fed rice crop; the farmers now practice two rice crops a year. The grazing area for the buffalo and cattle is limited which makes the traditional method of raising the ruminants difficult. The main feed resources for all these systems are native grasses, shrubs, legumes and tree leaves that are available in those areas. Especially, goats are susceptible to seasonal parasite burdens under poor management conditions, resulting in high mortality rates up to 50%. Native goats have high reproductive rates and are much cheaper than cattle and buffaloes, which make them very attractive and accessible to poor smallholder farmers.

A serious constraint to livestock production is the high animal mortality rate due to widespread incidence of animal diseases. More than 80% of chickens are said to die every year in upland village; sporadic disease epidemics frequently kill many of the pigs, and the mortality rate of buffalo calves due to internal parasites is estimated at 30 to 40% (FAO, 2005)

Livestock production has often been identified as an ideal livelihood activity for Lao farmers who are looking for ways of moving out of shifting cultivation, especially in upland areas.  The reasons for this have been presented elsewhere (Pravongviengkham, 1998; Hansen, 1998) but include:

§  Livestock can be sold at any time in a market that has a relatively constant demand and relatively stable prices

§  Ruminants such as goats, cattle and buffalo can walk for long distances to market

§  Livestock provide manure to sustain yields of lowland rice and home gardens

§  Livestock provide a relatively high return per unit of labor input

§  Larger livestock use feed resources that cannot be utilized for any other purposes

§  In many cases, livestock are the only means of capital accumulation available to farmers

§  Livestock are less susceptible to the climatic cycles of drought and flood and, unlike crops, can be sold to when there are extreme conditions, like at times of severe floods.

Potential for goat improvement

Most goats in Laos are grazed freely all year round in small groups in the forest and fallow cropland. Health problem and lack of feed seem to restrict enlargement of the herd. Farmers also tend to restrict the herd size in order to avoid excessive damage to crops, for which the owner is held responsible (Stür et al., 2002). In recent years goat management practices have been changing (Phengsavanh 2003), and vary from site to site depending mostly on land availability, labor and community regulations. The existing production systems include free-range, semi-rotational grazing, semi- free range system, and permanent grazing and tethering are found in the country. There is a comparative advantage for ruminant production in Laos because of the availability of large areas of suitable land.

Most goats are produced in extensive production systems with low capital and other inputs, particularly in hilly areas that are ideally suited to breeding and supply of weaned goats. The local breeds have high reproductive rates and are much cheaper than cattle and buffaloes, which make them very attractive and accessible to poor smallholder farmers. For the small-scale farmer, the goat has a number of attractive properties. As they are small animals, compared to a cow, their value is not very high meaning keeping goats has less risk. It is easier to find feed for a small animal and even small children can control them and they are a quickly maturing animal with a high fertility. Animals are regularly available for sale or other uses so herd size restoration is also quickly done. Goats, especially can maintain themselves well in poor areas with long dry seasons, where other ruminants cannot. Goat rearing requires a low labor input compared to large ruminants and cropping. (Carl et al, 2004).

Constraints and limitations on goat production

The results of the survey (Paper I), indicated that the constraints and limitations to goat production in Laos were:

• Due to the free grazing system, the high incidence of diseases and parasites are the main problem for smallholder goat production. These include internal parasitic infestation, especially in young kids after weaning. Heavy worm infestations are the cause of high mortality of kids, which can be up to 50 percent prior to weaning. Contagious ecthyma, an infectious dermatitis of goats that affects primarily the lips of young kids is the other problem. It can be treated with a little care at the time of an outbreak, but generally goats are severely affected and lose weight. Bloat is another concern and has been a cause of mortality.

• Feed shortage in both dry and wet seasons, especially in the areas of intensive crop production, where grazing land becomes limited. The long dry season also affects the productivity of the grazing areas. Animals gain weight in the wet season and lose weight in the dry season when they are susceptible to diseases.

• In many cases during the planting season, goats are tethered or confined in small areas where feed is limited, to avoid crop damage. In the dry season, the amount and quality of feed is low; and although goats are allowed to graze freely, they may have to walk long distances in search of feed

• All of these problems have a negative impact on growth and productivity of goats

• Lack of extension capability to promote improved animal nutrition and husbandry

• Lack of capital: access to credit by smallholders is generally difficult and expensive

Possibilities for intensification of goat production in Laos

There are several reasons for promoting more intensive systems of goat production in Laos.  The most important is the need to reduce production of greenhouse gases which are major contributors to global warming. Methane production from livestock is estimated to account for 37% of total anthropogenic emissions of this gas, two thirds of which arise from enteric fermentation in ruminant animals (FAO 2006).  Two factors have to be considered. One is the productive rate of the animals, and this is specifically an issue in Laos as the extensive grazing systems support only low rates of animal productivity.  It has been clearly demonstrated that the higher the growth rate the lower is the proportion of methane per unit of live weight gain (Leng 1991). This is an incentive for intensifying the present goat production systems. The second factor concerns the possibilities of modifying the rumen fermentation to reduce directly the proportion of the dietary energy converted to methane.   From a review of the literature, Leng (2008) arrived at the conclusion that the presence of nitrate salts in the rumen will act as a sink for the hydrogen produced by fermentation of carbohydrate such that the hydrogen will be converted to ammonia rather than methane. Results of unpublished recent research in Australia and the Netherlands (R A Leng, personal communication) indicate that the proportion of methane in the rumen gases of cattle can be reduced by 50% by feeding sodium nitrate instead of urea as the nitrogen source in low-protein diets based on rice straw and sugar cane. According to Leng (2008), the dietary conditions which favour utilization of nitrate to lower the production of methane are: a source of easily fermentable carbohydrate, a low content of soluble protein, an adequate level of sulphur and a source of bypass protein.

Sugar cane satisfies the need for a basal diet that is rapidly fermentable (contains 50% sugar in the DM) and is low in soluble protein (less than 1% in DM). It has been shown to support growth rates in cattle of over 700 g/day when supplemented with urea and rice polishing as a source of bypass nutrients (Preston et al 1976). The potential to grow sugar cane in Laos is very high and presently there are ongoing projects to establish several sugar cane factories in the central and northern regions of the country. It also is one of the highest biomass yielding plants

In the experiment reported in Paper II, there were no differences in growth rate between goats fed chopped whole sugar cane and those fed fresh Gamba grass; however, the DM feed conversion was much better on the sugar cane diet.

The foliage of cassava (Manihot esculenta, Crantz) is now considered to be one of the most appropriate sources of bypass protein in ruminant diets due to its content of condensed tannins that bind the leaf proteins in the processes of mastication (Wanapat 2008).  Several recent studies have shown major increases in growth rate in cattle when low-protein basal diets were supplemented with cassava foliage either in the fresh state (Ffoulkes and Preston 1978; Ho Quang Do et al 2002; Seng Mom et al 2001), as sun-dried foliage (Keo Sath et al 2008) or as leaf meal (Ho Thanh Tham et al 2008).  An additional benefit from feeding cassava foliage to goats is that the tannins appear to modify or control nematode infestations (Seng Sokerya and Rodriguez 2001).

There is some controversy as to the potential toxic effects of the hydrocyanogenic glucosides present in fresh cassava foliage and which can give rise to liberation of HCN. For this reason, sun-drying of the foliage has often been recommended as the preferred form of processing (Wanapat 2005). On the contrary there are several reports (Ffoulkes and Preston 1978; Seng Sokerya et al 2001; Theng Kouch et al 2003; Seng Mom et al 2001) in which cassava foliage was fed in the fresh state and where there were no indications of toxicity. There appear to be no reports in the literature of toxicity resulting from the feeding of fresh cassava to ruminants.

The experiment reported in Paper II showed not only that there was no toxicity from feeding the fresh cassava foliage but that growth rate and feed conversion were better on the fresh than on the sun-dried foliage.

Conclusions

·         There is considerable potential for increasing goat production in Laos as demand for meat is high both in local and export markets

·         Present management systems support only low productivity and are constrained by reducing availability of grazing land due to competition from food and cash crops

·        Future developments should consider the opportunities for intensification of the production system, which would have dual benefits of improved meat quality resulting from faster growth rates and improvements to the environmental damage through the potential for reduced emissions of methane. 

Acknowledgements

The authors gratefully acknowledge the Swedish International Development Agency (SIDA) for the financial supports of my survey, all farmers, the District Agriculture and Forestry Office of Xe Bangfai and Nongbok Districts, Khammuane Province, Laos for giving valuable information. We are also grateful the University of Agricultural Sciences (Uppsala), and to all staff members of Livestock Research Centre for valuable help during the field operation.

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