Factors influencing village cattle keeping, concept of balanced nutrients for ruminants and cassava foliage as source of bypass protein

Keo Sath

CelAgrid
Phnom Penh, Cambodia
keosath@celagrid.org

 

Factors influencing village cattle keeping

Livestock is always an important component of farming systems of small-holders farmers in Cambodia. Chantalakhana and Skunmun (2002) proposed the following classification in relation to the role of animals in providing a system of savings for rural farmers:

• Poultry offer a short-term or current saving account for daily petite cash needs,

• Pigs or small ruminants offer savings in the medium-term or semi-annual term to pay for relatively larger expenses such as clothes or educational needs for children;

• Large ruminants such as cattle and buffaloes serve as long-term saving or permanent savings account to provide biggest source of cash for very important family needs.

Rural farmers mainly grow crops as the primary commodity and they keep cattle for draft power and for manure as fertilizer for their crops. The number of cattle kept by farmers depends on the degree to which they can find local feed resources to feed their animals. Along the Mekong and Tonle Sap rivers, farmers keep Haryana breed because feed resources such as agriculture products and byproducts are available almost year round and this breed requires larger quantity and better quality of feed. Haryana was introduced into Cambodia in the 1960s. Local "Yellow" breeds are found in most regions of Cambodia and these breeds seem to survive better than Haryana under harsh conditions of food shortages and diseases including parasites. However, the crossing of Haryana with local breeds has become popular to improve production as well as draft power needed for growing rice

Keo Sath et al (2007a) found that most households kept 3-5 heads of cattle with the highest percentage being crossbreeds of the Haryana with local "Yellow" cattle.

Income generation and consumption

As sources of protein, livestock products continue to play a role in the average rural Cambodian diet. Maclean (1998) estimated that annual per capita consumption of livestock meat was about 17.5 kg in 1997, made up of 8 kg of pork, 6.5 kg of poultry, and 3 kg of meat from cattle and buffalo. Cattle are sold to slaughterhouses, which are mainly serving urban consumers, when they are no longer capable of farm operations, although rural households rarely buy any meat from slaughterhouses; they typically consume pork and beef at ceremonies and in some cases when animals die from an accident or diseases (Maclean 1998).

Cattle, buffaloes, and pigs are the primary sources of cash income for farming households. Pigs are directly kept for cash generation, whereas cattle and buffalo are primarily kept for draft power purposes. However, cattle and buffalo can also generate significant amounts of cash. Breeding animals generate cash through the sale of calves and draft animals can be hired out for land preparation. In addition to cash generation, cattle represent an efficient means of "storing" wealth, since they have long productive lifetimes (8-10 years for cattle), and in the case of cattle, can readily be sold for slaughter. It was found that selling an adult cattle would be enough to cover the loss of rainy season rice due to the increase in price of cattle which has occurred in recent years (Keo Sath et al 2007a).

Employment

Animal production in rural area provides year-round job opportunities especially for women, elderly people, and children in their spare time. In villages, it is very common to see women, children, and old people taking care of cattle, ether feeding, herding, cleaning, and burning of grasses to make smoke in order to disturb mosquitoes and insects away from animals, or other forms of animal care. It has been shown that women participate in the labor force and often make critical decision concerning crop cultivation and animal production (Parris 1992). For example, in India, it has been accepted that most farmers are women, and their role in livestock production is very significant (Rangnekar 1992) especially in dairying and small ruminant production. In Indonesia, women play important roles in small ruminant management as well as related decision-making (Wahyuni et al 1992). Thus, livestock production can be used to solve unemployment of family members, variations in cash income and preventing the migration of rural people to big cities. Children in villages usually spend their weekends tending and playing with farm animals.

Draft power and organic fertilizer

Animals play an important role in support of the sustainability of small-integrated farm agriculture production. In return the keeping of cattle serves as draft power for crop production and in providing manure as fertilizer for crops. The proper use of animal draft power and manure as fertilizer does not cause soil compaction, air and water pollution, or soil contamination. Using animal for draft power especially cattle is a way of recycling energy, while use of manure increases soil organic matter leading to sustainable agriculture production. Chemical fertilizers are generally expensive for small farmers and their extended use has proven to be deleterious to soil texture and quality. Animal draught power is appropriate, both economically and sociologically, since most farmers live in remote areas and own only small parcels of land, while family labor is generally available (Chantalakhana and Skunmun 2002).

Types of draft animals power in Cambodia

All work by animals in Cambodia is undertaken by pairs of animals, except for a few areas in the Northeast where ethnic groups sometime use single animals for plowing. This is in contrast with Thailand and Vietnam where single animals are usually used. Farmers in Cambodia like to have a pair of castrated males which similar height and condition. Maclean (1998) has described the different activities undertaken by cattle and buffaloes in Cambodia (Table 1).

Using by-products

The increase in the human population has lead to an increase in demand for food and therefore there is a need to plan carefully the feeding of livestock to avoid competition between humans and animals. However, in Cambodia farmers feed their animals with crop residues and agricultural byproducts. In the rural area, mostly farmers do not have the opportunity to purchase balanced feed concentrates or the ingredients to make feeds for their animals. Therefore, the cattle have to rely on crop residues, collected from the farm, or foliages of multi purpose trees, shrubs and grasses, which are harvested from the farms or roadsides.

Straw is considered by most scientists to be of little nutritional value because of its low content essential nutrients, and low digestibility, such that fed alone it does not support even the maintenance of ruminant animals. Farmers regard straw as a poor feed because cattle generally lose weight when fed straw without supplementation. However, there are ways to improve straw quality by treating with urea or lime (Wanapat et al 1985; Nuyen Xuan Trach et al 2001) or adding scums from sugar palm (Keo Sath et al 2007a).

Other factors

Other factors that influence village cattle production are the availability of specialized services such as veterinary care, markets for animals, preference for local sources of meat by urban consumers. Beside the factors mentioned above, rural farmers have also kept cattle to fulfill cultural aspects such as for bull fighting and cattle racing, practices which is are common in some countries of Southeast Asia. Moreover, in term of ensuring status and prestige, people who have a large number of cattle or have cattle which are "handsome" are regarded as being from a rich family.

Feed resources for ruminants in Cambodia

The availability of feed resources is determined by the land utilization pattern and it varies between regions. This is because the needs of the human population demand land to make shelter or to grow crop, thus grazing areas are reduced. Other factors are the nature of the local ecosystems, soil characteristics including terrain, availability of water, fertility, and the rainfall. Native grasses and shrubs are the main feed for cattle in Cambodia. Normally in the lowland area, cattle are grazed freely before crop planting or after harvesting, whereas in some areas feeding of cattle is based on hand-cutting of forages or grasses that are available in rangelands, forests, fallows and roadsides. Other sources of significant amounts of feeds are the crop residues in the locality, mainly rice straw. Normally, rice straw is collected and stored to feed cattle when other feeds are scarce, as in the period from crops planting time to harvesting. At these times, animals have limited or no access to grazing, while conditions of drought also influence availability of natural feed resources. Plant biomass that grows in the wet season is insufficient to feed cattle in the dry season. In the dry season, the protein content of the natural grazing falls often from 12-14% to about 6-8% (IAEA 2002) and the fibre content increases. However, the fibrous biomass is only usable as a major component of diets by ruminants, if it is supplemented with additional nutrients required for rumen microbial fermentative activity for its digestion (Leng  1997). Keo Sath et al (2007a) showed that the fruits and leaves of sugar palm, rain tree, bamboo, manila tamarind and cassava products are used when grass or crop by-products are not available in sufficient quantities.

Concept of balanced nutrients for the feeding of ruminants

Feeding strategies for ruminants based on locally available feed resources require the understanding of the relative roles and nutrient needs of two-compartment systems. Adem et al (2005) and Preston and Leng (1987) described how ruminant animals require two type of digestible protein; the first is degradable protein that is used by the rumen microorganisms to produce microbial protein and the second is the bypass protein that is digested in the small intestine and used directly by the animal through enzymatic digestion in the intestine. The microbial protein alone is sufficient to meet the needs of cattle at near maintenance. But young growing cattle and lactating cows need additional "bypass" to complement the microbial protein and thus ensure their needs for metabolizable protein.

Smallholder farmers in developing countries have limited resources available for feeding to their ruminant livestock. It is difficult for them to formulate the basal diet according to the requirement for production; and generally the only opportunity is to use whatever is available at no or low cost. Therefore, the strategy for improving production should be to optimize the efficiency of utilization of the available feed resources and thereby attempt to maximize animal production.

Therefore, as described by Preston and Leng (1987) and Leng (2004), when considering way to optimize the utilization of feed resources for ruminants it is necessary to apply basic concepts that include:

• Ensuring optimum conditions for microbial growth in the rumen to make this part of the digestive system of the animal as efficient as possible by providing macro and micro minerals and sources of ammonia

• Providing a protein meal that is relative slowly degraded by microbial action such that a proportion of the dietary protein enters the intestine for enzymic digestion

• Modifying the rumen microbial ecosystem (eg: defaunation by oil drenching) to minimize protozoa that prey on bacteria and reduce protein flow to the intestine.

Nutritional needs of rumen microbes

The role of individual species of the bacteria, protozoa and fungi in the rumen has been given recent attention through studies to ensure that their activities are regulated to improve the efficiency of feed utilization. For rumen microbes to be adequately fed requires optimum levels of rumen ammonia in the range 200-250 mg NH₃-N /litre of rumen fluid. The optimum level of rumen ammonia helps to improve digestibility, feed intake and flow of microbial cells and therefore protein to intestine (Leng 2005). The diet is the main source of nutrients for the microbes and the nutrients supply will be determined by the level of feed intake and concentration of nutrients contained in the feed. According to Leng (1997), growth of microbial cells in rumen requires a source of fermentable carbohydrate, N compounds for synthesis of protein, minerals and vitamins. Soluble carbohydrates and smaller molecules of oligosaccharides, contained in plant, provide the energy source for rumen microbe after forages are ingested (Bakrie et al 1996). This energy permits microbes to use ammonia and amino acids from fermenting of fibrous feed, while saliva flow helps to ensure not only buffering capacity to maintain the rumen pH but also acts as part of the system of nutrient recycling. Bryant (1973) claimed that ammonia could be the sole source of N for the synthesis of protein and other nitrogenous compound in the majority of rumen bacteria. Ammonia can be met from urea, other nitrogenous compounds or soluble proteins (such as leaf protein and seed protein). Urea can supply the microbes with ammonia and can be incorporated at appropriate level in ruminant diet to ensure adequate levels of rumen ammonia. It is usually sufficient to ensure an intake of between 50 and 100g urea/day from a molasses-urea multi-nutrient block to provide rumen microbes with their requirements of ammonia on low N pasture (Leng  1997).

Minerals are required for various aspects of microbial activity. Deficiency of some minerals such as sulphur, phosphorous, calcium is considered to be important for digestibility of forage. Growth of fungi is highly dependent on sulphur availability (Akin et al 1983); this may present a major constraint to digestion of poor quality forage. Hogan (1996) described that the needs of phosphorous (P) for cellulolytic bacteria are higher than for other bacteria. Whereas, Calcium (Ca) demands are for formation of bone and other tissues and in milk secretion which suggest that the main needs of the animal for Ca relate to the tissues rather than the rumen microbes (Bakrie et al 1996). Macro and micro mineral can be supplied through multi-nutritional blocks or small amount of green forage supplements.

Keo Sath et al (2007b) showed that cattle fed rumen supplement (providing urea, sulphur, and other minerals) with poor quality roughage (rice straw), gained in live weight at 200g/day.

Bypass protein

Many research projects have shown that feeding a protein meal, which has "bypass" characteristics, has a positive effect on ruminant production such as wool, meat and milk. Bypass protein or "escape protein" is a commonly used term to refer to dietary protein that is not degraded in the rumen. The purpose of supplementation with a protein meal is to provide nutrients that are deficient in the basal diet and which are needed for productive purposes. The selected supplement should not reduce feed intake and utilization of the basal diet but instead have potential for enhancing them (IAEA 2002). The amount of protein and amino acids that escape rumen degradation varies greatly among different feeds, depending on their solubility and rate of passage to the small intestine. The benefit of protecting protein from rumen degradation is to enhance supply of these valuable proteins to the productive animal and reduce nitrogen loses as urea in the urine (Annison  1981).

Protection of protein to create by pass protein

Protection of protein from ruminal degradation enables more amino acids to reach the intestine and therefore provide more absorbable amino acids. Earlier research was concerned with effects of treatment with heat and chemical, coating with lipids and identification of naturally protected protein (Ferguson  1975). Recently attention has been given to the benefits of low levels of certain natural components of plants such as tannins, which bind with proteins to form complexes that are resistant to microbial attack in the rumen, but which are dissociated in the acid conditions of the stomach to become available to digestive enzymes in the intestine (Barry  1983). A high concentration of tannin, above 5% of diet dry matter, becomes a serious anti-nutritional factor (Mcleod 1974) reducing intake and digestibility (Reed et al 1982; Onwuka 1992). However, Barry (1983) and his colleagues demonstrated that a concentration of condensed tannin of 2-4% of diet dry matter appears to protect the protein from microbial attack in the rumen. Thus, a low level of tannin in plant materials has been accepted to be able to protect protein of forages and allow a higher efficiency of feed utilization by the animal.

Cassava as dual-purpose crop

Cassava or tapioca is a tuber crop grown widely in tropical and sub-tropical area. Cassava has been given considerable attention by a number of research institutes in developing countries because it is easy to grow and can survive on soils with poor fertility, where other crops would fail (Howeler and Cadavid 1990). It survives in soils with prolonged water deficit (Alves and Setter 2000; Wanapat et al 1997) and is tolerant to acidity (Cock and Howeler 1978). It has high level of energy from roots and protein from the leaves, which both can be used for human and animal food. In addition, the recent work by Miech Phalla (2005), showed that stems can be used as fuel in a gasifier to generate electricity. The main product of mature cassava plant (at 12 months after planting), expressed as percentage of the whole part, were estimated as 6% leaves, 44% stems, and 50% tubers (Devendra 1977). Cassava can be managed as a semi-perennial forage crop with high yields of fresh foliage of up to 20 tonnes/ha/harvest (Preston et al 2000) with repeated harvesting at 2-3 month intervals. However, this practice affects roots yield and a lower yield of stem in case of using them for gasification. Other options commonly practiced are to cultivate cassava for root production by collecting leaves when harvesting root. Gomez and Valdivieso (1984) reported that leaf dry matter yields at root harvesting were from 1.2 to 1.8 tonnes/ha.

Chemical composition of cassava foliage

Numerous studies have shown that the protein in cassava leaves is more than 20% in DM basis (Reed et al 1982; Wanapat et al 1997; Doung Nguyen Khang and wikorsson 2001). The crude protein level in the cassava leaves is almost three times higher in the leaves than in the petioles (Keo Sath et al 2007b). Cassava is also a rich source of most minerals, particularly Ca, Mg, Fe, Mn, and Zn and is also rich in ascorbic acid, vitamin A, and contains significant amounts of riboflavin (Ravindran 1991). However, there is a significant variation in nutrient content between seasons of growing (AFRIS 2004), cassava varieties, stage of maturity (Ravindran and Ravindran 1988) and soil fertility (Moore 1976).

Secondary compound in cassava

Hydrocyanic acid is considered as an anti-nutritional factor that is released when fresh cassava foliage is fed to animals. Both leaves and roots of cassava contain HCN. The HCN contain of fresh cassava varied from 125 to 854 mg/kg fresh basic (Chew 1972; Ravindran 1991; Wanapat et al 2000b; Ngo Tien Dzung 2003; Murugueswari et al 2006). The variation is due to variety and management of cassava foliage. The HCN concentration, produced after the action of hydrolytic enzymes occurring in the plant on the cyanogenic glycosides, is influenced by the nutritional status and age of the plant (Ravindran and Ravindran 1988). The bitterness is cassava leaves is also related to the presence of cyanogenic glucosides. Cadavid et al (1998) reported that supplying N, P and K fertilizer to cassava significantly increased root and top biomass and reduced root HCN content. De Bruijn (1973) found that leaves produced during drought were reported to have high cyanide content. There are techniques to reduce HCN levels in both leaves and roots such as wilting, ensiling, sun drying, and boiling to make then safe for use as food for humans and animals (Ravindran 1991; Wanapat, et al 1997; Khieu Borin 2005, Murugeswari et al 2006).

The presence and role of condensed tannins in cassava leaves was discussed by Reed et al (1982). Tannins in cassava leaves have been shown to increase with maturity (Gomez and Valdivieso 1984; Ravindran and Ravindran 1988) and also to vary between cultivars (Padamaja 1989). It was reported that tannin content in fresh cassava leaves varied from 30 to 50 g/kg DM (Ravindran 1993) and from 32.6 to 43 mg/kg in sun-dried cassava leaves (Wanapat 2003; Netpana et al 2001). Numerous studies have shown the potential of the tannin content in cassava leaves to play an anthelminthic role for the control of nematode parasites in ruminants (Seng Sokerya and Preston 2003; Neptpana et al 2001; Le Huu Khoung and Doung Nguyen Khang 2005).

Potential of cassava foliage as source of bypass protein for ruminants

Feeding fresh cassava foliage to cattle and goats did not show any effect of toxicity from HCN or tannin, when the cassava was managed as semi perennial forage with repeated harvests at 50-80 day interval under fertilization (Seng Mom et al 2001; Seng Sokerya and Rodriguez 2001; Theng Kouch et al 2003). In fattening cattle, Ffoulkes and Preston (1978) reported that the fresh foliage could be used as the sole source of protein and fibre for supplementing a liquid diet of molasses-urea, supporting growth rates of more than 800 g/day in fattening cattle. Similarly, Seng Mom et al (2001) reported that when fresh cassava foliage was given to local "Yellow" cattle fed rice straw and rumen supplement, the daily weight gain increased from 210 to 302g/day while Le Huu Khoung and Doung Nguyen Khang (2005) reported that increasing levels of fresh cassava foliage increased total DM intake and rate of live weight gain from 138 to 160 g/day.

In Thailand, cassava hay has been successfully used for dairy cattle to improve milk yield and quality and reduce the need of concentrates (Wanapat 2001). Promkot and Wanapat (2003) estimated that cassava hay has a similar content of rumen undegradable protein as cottonseed meal (considered to be one of the best sources of bypass protein according to Preston and Leng 1987). Chanjula et al (2004b) reported that increasing the level of cassava hay as a roughage source could enhance rumen ecology by increasing cellulolytic and proteolytic bacterial populations and fungal zoospores while the protozoal population was decreased.

Keo Sath et al (2007b) reported that increasing levels of sun dried cassava foliage led to significant increases in total dry matter intake and daily weight gain of cattle fed untreated rice straw and a rumen supplement. Daily weight gain increased from 201 to 402 g/day and feed conversion was better with increasing levels of protein from sun-dried cassava foliage in the diet. The responses were linear over the range of cassava crude protein intakes from 0 to 1.6 g crude protein/kg live weight.

Conclusions

It is concluded that:

• Cattle keeping is an integrated part of faming systems in Cambodia and is closely associated with the livelihoods of farmers as they are a source of protein-rich food, family income, and jobs for those without formal employment opportunities.

• Feeding strategies for ruminants based on locally available feed resources require understanding of the relative roles and nutrient needs of microorganism in the rumen and host animals.

• Increasing levels of sun dried cassava foliage supplementation leads to significant increases in total dry matter intake and daily weight gain of cattle fed untreated rice straw. The response to cassava foliage protein is linear over the range of 0 to 1.6 g crude protein/kg live weight.

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