Ensilaging of tropical forages with particular reference to South East Asian systems.
Department of Veterinary Services, 8th Floor, Chase Perdana Building, off Semantan Road, Damansara Heights, 50630 Kuala Lumpur, Malaysia
[Paper presented at the XIIIth International Silage Conference, 11-13th September, 2002]
Ruminants are important in South East (S.E.) Asia with cattle providing the main source of meat, milk, draft power and a means of livelihood for farmers. Ruminant production systems have been differently indicated for the whole region ( Mahadevan and Devendra, 1986, cited by Ridzwan, 1996) as well as for Thailand alone (Shelton and Phaikaew, 1998). In this paper, these are categorised as traditional village system; specialised, commercial farming system; ranching system; and integrated livestock-tree crop system.
Most ruminants reared throughout the region are in the hands of smallholder farmers who usually rear few animals and practise the traditional village system. This system, which is the most widespread, exist on lowland rice production areas, upland cropping areas, community grazing grounds and other marginal land areas. Animals are very much dependent on the consumption of green forages available on marginal land, including fallow cropping areas, and roadsides generally through free range grazing, tethering or cut-and-carry. The animals also greatly depend on natural browses, crop residues and agricultural by-products, especially during drought when green forage growth becomes limited. Rice straw is a very important crop residue for feeding smallholders ruminants in many of these countries.
Over the last 2 decades, some progressive farmers, including new entrepreneurial livestock producers, have gone into specialised, commercial production such as dairying and beef fattening in feedlots. These farmers rear more animals under semi-intensive and intensive systems. This results in new feed and feeding activities being introduced such as cultivation of pastures and fodder crops on the farm or in backyard/home plot/private plot, which may include leguminous browse shrubs/trees, e.g. leucaena (Leucaena leucocephala), sesbania (Sesbania grandiflora) and glyricidia (Glyricidia sepium); fodder conservation; as well as purchase of commercial feed resources. The latter include crop residues, agricultural by-products, agro-industrial by-products, grains, compounded feed and even conserved fodder in the form of hay and silages. This specialised commercial farming system ranges from small- to large-scale. Small backyard dairy and beef units are common in Indonesia, Philippines and Thailand with the grasses, guinea (Panicum maximum) and napier (Pennisetum purpureum), being supplemented with leucaena, glyricidia and various by-products (Reynolds, 1998). In Malaysia, there are currently 741 dairy farmers registered with and marketing their milk through 36 government-operated dairy industry management centres, with another 30% of this number of farmers marketing milk on their own. In the case of beef, 64 small farmers (fattening less than 100 heads per annum), 75 semi-commercial farmers (fattening 100 to 599 heads per annum) and 13 commercial farmers (fattening more than 600 heads per annum) had fattened a total of 80, 535 heads in feedlots during 2001.
A number of small- to large-scale ranches, more simply called farms in the region, have also developed in Indonesia, Thailand, Philippines and Malaysia. These ranches, either governmental or commercial, are usually based on cultivated pastures and fodder crops and practise semi-intensive and/or extensive husbandry system. Government operated ranches are usually for nucleus breeding, multiplication of stock for supply of heifers to farmers, research as well as training and extension. In Malaysia, there are 10 large scale beef and dairy ranches, covering close to 10,000 hectares of land; 5 small scale goat and sheep ranches, covering about 1200 hectares; as well as a few small scale deer and ostrich ranches where cultivated forage also plays an important part in the daily diet.
Grazing of livestock under tree crops has existed for a long time in certain parts of the S.E. Asian region. More recently, a large-scale system has developed in Malaysia where electric fencing enables the systematic grazing of undergrowth on a rotational basis under plantation crops, chiefly oil palm ( Elaeis guineensis). The oil palm plantations in the country, occupying an estimated total of 2.8 million hectares, thus represent an important area where sustainable, systematic beef cattle/tree crop integration is undertaken with undergrowth vegetation as the major feed resource (Chin, 1998). Currently, there are 174,000 heads of cattle reared over a total of 146,527 hectares of oil palm under this system. Integrating of ruminants into plantation crop is expected to be potentially a major production system in southern region of Thailand where rubber, oil palm, fruit trees and coconuts occupy almost 2 million hectares (Shelton and Phaikaew, 1998). Indonesia with its vast hectarage of oil palm plantations has also the potential of adopting this systematic beef cattle/tree crop integration system.
This paper discusses the ensilaging of forages in relation to the various production systems existing in S.E. Asia. Forms of forage include natural and improved grazing lands, hay and silage, fodder crops, crop residues, and supplementary feeds, such as grains or by-products (Harris, 2000) and, for this paper, the forage resources include cultivated pastures and fodder crops, crop residues as well as agricultural by-products.
CURRENT ROLE AND IMPORTANCE OF SILAGE
Identifiable roles of ensilaging and silage
There are four identifiable roles played by ensilaging and silage. Primarily, these are to build up feed reserve for utilisation during periods of feed deficiency; to supply routine feed to increase productivity of animals; to utilise excess growth of pasture for better management and utilisation; and, to store and enable extended use of potentially unstable material. These are similar to advantages already linked to silage use (Cowan, 1999).
As feed reserve for utilisation during periods of feed deficiency
The earliest role of silage in S.E. Asia is as reserve for feeding during periods of feed limitation, attributable to drought or flood. In Thailand, silage making is one of the fodder conservation methods to overcome feed shortage in dry season and silage has been produced for many years by government research and field extension stations and distributed to farmers, mostly dairy farmers (Poathong and Phaikaew, 2001). Ruzi grass (Brachiaria ruziziensis), purple guinea grass (P.maximum), atratum grass (Paspalum atratum), sorghum (Sorghum discolor) and maize (Zea mays) are used in the ensiling. In Vietnam, it is reported that, while small farmers are interested in silage, it is the medium and big size farms that are forced to keep silage during winter dry season (Ly, 1998).
In Malaysia, production of grass silage as drought reserve has been undertaken since the nineteen sixties (Chin and Idris, 1999) although mostly on an irregular basis and limited scale, especially in the early years. However, a more organised ensilage program was carried out, from 1983 to 1985, on a government farm institute in the southern state of Johore by the Department of Veterinary Services (DVS), in co-operation with the New Zealand Dairy Board, using surface stack pile system of ensiling. About 400 tonnes of grass silage from signal grass (B. decumbens), guinea grass (P. maximum), kazungula grass (Setaria sphacelata cv Kazungula) and napier grass (P. purpureum) were produced (Chin and Idris, 1999; Chin, 2001). Currently, an ongoing silage making activity, introduced in 1991, on 2 to 3 government farms as well as on grazing reserves involves mechanised wrapping of small round bales with plastic film (Koon, 1993; Chin and Idris, 1999; Shariffah Noorhani et al., 1999; Chin, 2001). An estimated total of 300 tonnes of this plastic film wrapped bale silage have since been achieved with about 500 bales, equivalent to 15 tonnes, of the silage being annually produced. Ensiling work undertaken on government farms also uses wooden and concrete bunker silos as well as excavated earth trenches. Another ongoing activity, initiated in 1994, in Trengganu State (Chin and Idris, 1999; Chin, 2001) as a governmental project but now in the hands of farmers, ensiles sweet corn (maize) stover in plastic drums for supplementing beef and dairy cattle forage needs during drought and flood. Annually, an estimated 120 tonnes of sweet corn stover silage are produced (Idris et al., 1999). The oil palm fronds, or OPF, have great potential for use as a roughage source or as a component in compound feed for ruminants (Wan Zahari et al., 1999). Although on a limited scale, some dairy farmers in Malaysia have used OPF silage for feeding in times of need. Ensilage of fronds from nepah palm (Nepa fruticans), from which nepah palm sugar is extract, has also been studied (Abdalla et al., 1998; Abdalla et al., 1999; Abdalla et al., 2001). The fronds serve as useful forage for livestock located where these palms thrive, particularly the low-lying areas in the wetter part of the region, such as in Malaysia and Indonesia.
As routine feed to increase productivity of animals
Silage is also routinely fed to increase productivity of beef and dairy cattle by providing nutrients necessary to nutritionally balance existing diets. A commercial feedlot in Supanburi Province, Central Thailand utilises silages made from purple guinea grass (P. maximum), maize and pineapple waste as part of the ration for fattening cattle (Phonbumrung and Khemsawat, 1998). Annually, about 403 tonnes of silage dry matter from the purple guinea grass alone are reportedly produced, using an earthwall above- ground bunker system, sufficient for 933 heads of feedlot cattle for 180 days. In Philippines, corn silage, produced through surface stack pile, is crucial to the commercial cattle operation in Sarangani Province, Philippines, allowing it to maintain a population of 410 head of 2-year old bulls and heifers, culled cows, fattening bulls and steers at any given time in feedlot, in conjunction with the breeding herd raised on pasture (Montemayor et al., 1999). When the corn crop was poor in 2000, the operation turned to using banana rejects for ensilage, in fish/prawn feed bags with plastic lining (Montemayor et al., 2001). Average daily live-weight gains of 1.11kg was obtained from feeding the banana reject silage-based diet that included para grass (B. mutica), concentrate and molasses; and this figure compares favorably with the 1.23 kg obtained for a similar diet using corn silage.
Between 1985 to 1986, DVS and the German Technical Aid (GTZ) Agency jointly initiated, in Kelantan State, Malaysia, a project among dairy farmers to produce silages from 3 different fodder crops, namely napier grass (P. purpureum), forage sorghum (Sorghum almum), and maize for daily supplementation of dairy cattle to improve their productivity. Silos used were small round vertical concrete silos, measuring 2 metres in diameter and 3 metres in height, each capable of producing about 7.5 tonnes of silages. Production totaling 30 tonnes of napier grass, 66 tonnes of maize and 250 tonnes of forage sorghum silages was achieved during the 2 years (Chin and Idris, 1999). Farmers in the project reportedly increased monthly milk sales from 630 litres in January 1985 to 2533 litres in April 1986 (Wan Rahim et al., 1986), seen as a positive effect from silage feeding. This positive effect on milk production from silage has also been confirmed in a subsequent study. Sorghum silage fed ad libitum and with guinea grass (1:1 ratio), together with 6 kg/day concentrate, caused significantly higher milk yields in Sahiwal-Friesien cows in mid-lactation of 7.93 and 7.54 kg/day respectively as compared to the 7.01 kg/day from consumption of a ration that has only guinea grass fed ad libitum, with equivalent concentrate supplementation (Aminah et al., 1992; Aminah et al., 1999 ).
Recently, in Malaysia, efforts are made on government farms to feed silage to upgrade the nutrition of livestock so as to improve their productivity. A beef farm in N. Sembilan State, ensiled pasture grasses, in a large sized concrete bunker, between 1997 and 1998. Since 2000, a dairy farm in Johore State has been making corn fodder silage in plastic drums for feeding under an ISO Quality Accreditation exercise. The Agriculture Department, Malaysia, has recently undertaken a project to fatten local indigenous and crossbred cattle with rations containing corn stover silage, ensiled in special, large plastic bags and plastic drums, getting reasonable good live-weight gains (Ng, E.G., personal communication). An existing large-scale commercial feedlot in Kempas, southern Malaysia, although mostly feeding fresh pineapple waste as part of a ration for fattening cattle, has at one time ensiled the waste in large vertical silos to take advantage of its abundance. Over the last one and a half years, kenaf or Indian hemp (Hibiscus cannabinus) silage has been produced in plastic drums in Malaysia (Chin, 2001; Chin et al., 2001). Kenaf has excellent crude protein content and is being studied concerning its feasibility as commercial high protein forage feed, in the form of green fodder, silage, hay as well as processed dried feed. Besides its use in times of need, some dairy farmers now collect fresh OPF daily from nearby oil palm holdings as a regular forage resource. These farmers are seriously looking at the potential of using ensiled OPF, either self produced or purchased, to reduce daily collection effort and time. It has been reported that ensiling improved the feeding value of OPF; no reduction in its nutrient contents being observed while the rate of degradability of its water soluble fractions was increased (Islam et al., 1998).
As a means to utilise excess growth of pasture for better management and utilisation
Ensilage of excess growth of pastures, natural or cultivated, will also secure an all year round supply of forage feed. In the tropical wet areas of S.E. Asia, heavy rainfall brings about very rapid regrowth of pastures, quickly leading to overly matured poor quality herbage and excess growth. In Malaysia, for instance, under the Critical Pasture Management and Utilisation (CPMU) concept, fast growing, aggressive, permanent grasses such as signal grass (B. decumbens), humidcola or koronivia grass (B. humidicola) and Mardi digitgrass (Digitaria setivalva) are defoliated as young as 1718 days of maturity under good rainfall conditions to get the best nutritive value (Choo et al., 1993; Chin, 1995). Thus, such grasses easily become "overly matured". Ensiling is a good option to utilise the excess forage if stocking density is not increased and hay making particularly during the rainy period is also not practical. Harvesting excess growth for ensilaging enables proper management of these pastures as well. Some of the pasture-based ensiling activities described for Malaysia have partly taken advantage of excess growth.
As a means to store and enable extended use of potentially unstable material
Basically, ensilaging of grasses, crop residues and agricultural by-products, described above, also represents another important role where the ensiling process enables extended use of forage resources that are perishable and unstable which, unless dehydrated or ensiled, can only be for immediate or at most very short term use. Since many of these have high moisture contents, sun-curing is difficult especially in the tropical wet areas of the S.E. Asian region and artificially drying may be costly or unavailable.
Importance of silage in relation to animal production systems
Overall, the role of silage as feed reserve is not important in the traditional village system leading to a general lack of adoption by smallholder farmers under the system. This is because, in many parts of the region, these smallholder farmers are still able to feed browses, crop residues and agricultural by-products during dry season. It is noted that during the dry period in Thailand, when green forages are scarce, crop by-products and farm wastes represent the important sources of feed for ruminant livestock (Khajarern and Khajarern, 1985). Similarly, during dry season, Thai dairy farmers have enough agriculture by-products such as rice straw, corn stover and pineapple waste for dairy cows (Poathong and Phakaew, 2001). In Philippines, in smallholder farms where livestock fodder such as crop residues and weeds abound and can be used conveniently without cost involved, silage production/utilisation has not found a place; but, in some areas, where green corn is the major product and farmers raise two or more ruminants or in small-scale dairying, silage may find a niche on smallholder farms (Lanting, E., e-Conference communication, cited by t Mannetje, 1999a). The latter is proven in the case of smallholder farmers in Malaysia undertaking sweet corn stover ensilage activities in the state of Trengganu.
Interest in silage as feed reserve is limited to government ranches or institutions as well as progressive farmers undertaking specialised, commercial dairying or beef fattening in feedlots who see the importance of and need for readily available feed resources which can be efficiently utilised and can ensure feed security throughout the year. Silage as a routine feed to increase productivity of animals has gained in importance in the region although actual cases are still small. These cases, found in the Philippines, Thailand and Malaysia, indicate that farmers now realise silage can play a significant role as part of the routine diet of ruminants. In the Philippines, the benefits of silage cannot be overemphasised particularly for commercial cattle operations and in dairying, where it has great economic benefits (Lanting, E., e-Conference communication, cited by t Mannetje, 1999a). The importance of storing potentially unstable material to enable their extended use is well recognised by the more specialised commercial farmers but very few smallholder farmers are taking advantage of it, preferring to utilise forage resources in the form available to them. The importance of ensilaging as a means to utilise excess growth of pasture for better management and utilisation is also not fully realised on pasture-based ranches in the region and in many instances pastures are seen to be allowed to become overly matured, thus deteriorating into poor quality swards which are either useful only as roughage or mowed down and wasted. Presently, silage has not become important under the livestock-tree crop integration system. It is obvious that feeding forage resources fresh, or in the form produced/obtained, is more important than feeding these after conservation. This is similar to the situation in India, where preference by most farmers to feed fresh hampers adoption of silage (Rangnekar, 1999).
KEY FACTORS FOR SUCCESSFUL USE OF SILAGE IN ANIMAL PRODUCTION SYSTEMS
The following are considered as key factors for the successful use of silage in the animal production systems in S.E. Asian region. Some of these are similar to reasons identified (t Mannetje, 1999b) as causing non-adoption of the silage technology in the tropics; the main ones being lack of know-how; lack of finance; silage making considered as cumbersome and labour intensive; benefits accrued do not commensurate with effort and time; animals having low genetic potential for production; cost and trouble of silage making does not provide adequate returns; lack of farm planning; and lack of available feedstuffs of good quality for ensiling.
The most crucial factor is that farmers must, in the first place, have a felt need for its use. In Thailand, a positive factor seen to affect potential for adoption of silage on small holder farms is that farmers realised that lack of good quality roughage in the dry season was their main constraint (Nakamanee, 1999). Another factor is the level of commitment from development/extension workers as well as farmers to make and/or use silage. There are cases where silage making and use have stopped because of lack or decline in level of commitment due to lack of or waning interest, not clearly defined policy, personnel attitude and even withdrawal of technical assistance.
Low investment costs and ability to give rapid and significant returns on investments are factors for the ensiling system to be suitable for smallholders in the tropics (Machin, 1999). In India, most farmers felt that benefits were not commensurate with the effort and time spent for ensiling (Rangnekar, 1999) and the same is felt by many smallholders in S.E. Asia. Thus, cost: benefit ratio will be a key factor that determines successful use of silage .
Land and resource availability
If silage needs to be prepared by the farmer from pastures and fodder crops, then land must be available for their cultivation as well as for placement of silo(s). Availability of the 4 M (Material, Money, Machinery and Manpower) is integral to the success of any enterprise, including silage making and use. As noted, if the need to produce own silage arises, then availability of resources, such as equipment, labour and finances, as well as technical assistance become considerations in the first management decision (Ojeda, 1999). Firstly, for successful adoption of silage making on smallholders farms, farmers must have sufficient material available locally to be ensiled (Nakamanee, 1999). Capital is also crucial. Even if a farmer intends to purchase ready made silage for use, he must have available funds. Funding is also important for scientists and extension workers to develop appropriate technologies and effectively transfer these to farmers.
Making of silage is not difficult, but the program depends on having the equipment readily available (Regan, 1999). This has been a major factor hampering the adoption of silage making technology, particularly for large-scale production and utilisation, in S.E. Asia. Suitable trucks, e.g. tipping lorries, tractors and equipment for harvesting/collection, delivery and compacting must be sufficiently available to allow ensiling to be completed within the shortest possible time. Adequate manpower is similarly emphasised.
Technology and technical know-how
Appropriate technology for silage making and use that suits the type or scale of livestock production system should be made available. Preference of 53 Thai farmers in the choice of 4 types of silos were demonstrated to be 38%, 31%, 23% and 8% respectively for bunker silo; plastic bucket, black polythene bags of 40-kg capacity and plastic bags of about 800kg capacity ( Nakamanee, 1999). On the other hand, ensiling in black plastic bag is reported as the method widely used on Thai dairy farms due to its convenience for filling, packing, sealing, handling and feeding out (Poathong and Phakaew, 2001). In Malaysia, plastic drums have become popular because, besides the convenience for use, these are not easily gnawed through by rats, causing spoilage, as when using plastic bags or plastic film wrappings. Chopped OPF were ensiled in plastic drums of 100 litres capacity (Wan Zahari et al., 1999) while 128-litre drums were used for ensiling corn stovers (Idris et al., 1999) and kenaf (Chin et al., 2001).
Lack of knowledge of silage making principles by the people and specialists involved in livestock farming has been identified as a limitation in the production of silage (Ojeda, 1999). It has also been noted in central and western India that most extension officers were aware of silage making processes and have basic information, but lacked in-depth knowledge and practical experience, with only 15% having the latter (Rangnekar, 1999). This situation is also quite true for the S. E. Asian region. Farmers also need technical know-how to efficiently and effectively make and use silage. Accurate information and data related to technical parameters in the production and use of silage pertaining to the S.E. Asian region are thus very important and these can be provided through proper research. Many farmers think silage making is cumbersome and labour intensive but, in fact, Thai farmers learning to make it found it neither difficult nor complicated (Nakamanee, 1999). Provision of training and extension service to farmers is thus very important to ensure successful use of silage.
Animal type and number
The type and number of livestock to receive silage can determine the success in its use. The need for silage making is more significant for dairy cattle, where demand for uniform and high quality feed is of great importance (Aminah et al., 1999). This is also true for feedlot cattle. Silage feeding usually does not provide sufficient returns in the case of low milk yielders and cattle with poor potential for growth. Number of animals, level of inclusion in the total ration and length of feeding period determine the quantity of silage a farmer needs to make or purchase and this will help him decide whether or not he wants to use silage. For instance, most dairy farmers in Thailand are not adopting silage making because the small quantity produced is not enough for their dairy cows during the dry season (Poathong and Phakaew, 2001). On the other hand, having small animal units is also a constraining factor that prevents farmers selecting silage as a feed option as the cost: benefit ratio is not impressive due to small size of the animal units (Syed Hassan, 1999).
Quality of silage will determine successful silage use and inclusion of additives as well as other treatments, e.g. chopping, can enhance silage quality to improve use. The suitability as silage (Table 1) of six tropical grasses, maize, sorghum (Sorghum bicolor) and forage sorghum ( S. almum), without or with 4 % molasses (Aminah et al., 1992), and common guinea grass (P. maximum cv. typica ) (Mohd. Najib et al., 1999) has been determined. Silage from the latter, at 6 weeks regrowth and ensiled for 1 month, has 12% crude protein (CP), 22.7 % crude fibre (CF) and 8.2% ash. Values of 4.3 megajoules (MJ) net energy (NE) and 24 gm. digestible crude protein (DCP) per kg. dry matter (DM) for napier silage; 6.6 MJ NE and 50 gm. DCP per kg. DM for maize silage; and 5.7 MJ NE and 30 gm. DCP per kg. DM for forage sorghum silage have been obtained (Wan Rahim et al., 1986). Corn stover, after harvest of matured cobs at 75 days of growth, contained 9.6% CP and 7.82 MJ/kg metabolisable energy (ME) and, after ensiling, these values decreased to 8.2% CP and 5.86 MJ/kg ME respectively (Idris et al., 1999). Comparable CP concentration has been obtained earlier during nutritive evaluation of sweet corn stover silage for growing lambs (Yacob et al., 1992). Chopping prior to ensiling improved fermentative quality of napier grass (P. purpureum) silage by lowering pH and ratio of volatile basic nitrogen to total nitrogen (VBN:TN) and increasing lactate content (Shinoda et al., 1999).
Fermentation characteristics, palatability and effect on animal performance (Abu Hassan and Ishida, 1991; Ishida and Abu Hassan, 1997; Oshio et al., 1999) as well as voluntary intake and digestibility (Wan Zahari et al., 1999) of OPF silage have been determined. A typical profile of OPF silage quality is shown (Table 2). Fronds from nepah palm (Nepa fruticans), with CP content of 5.4% on dry basis, are known to make poorer silage as compared to OPF, which has CP content of 7.9% on dry basis (Abdalla et al., 1999). With addition of 30% molasses, the quality of nepah frond silage was improved, becoming comparable to that of untreated OPF silage.
Table 1. Characteristics of grass and fodder crop silages.
Forage resource types
Simple silage, without molasses
Water soluble carbohydrate
P.maximum cv. typica2
Sources: 1Aminah et al. ,1999 2 Mohd. Najib et al., 1999
Table 2. Chemical composition and fermentation characteristics of OPF silage.
Dry matter (DM) % 30.1 As % of DM: Crude protein 6.7 Organic cell contents 20.8 Neutral detergent fibre 73.2
pH value 3.78 Total acids (% DM) 3.68
Composition of acids (%):
91.0 Acetic acid 6.1 Propionic acid 0.1 Butyric acid 0.9
Source: Anon, Malaysian Agricultural Research and Development Institute (MARDI), Malaysia.
Fresh kenaf fodder has CP content of 22.1-23.2% and ME of 9.88 MJ/kg -10.54 MJ/kg at maturity of 4 - 6 weeks growth (Chin et al., 2001). Initial work shows kenaf silage has good chemical composition and nutrient profile (Table 3). Good quality baled kenaf silage containing 16% CP, 44.6% acid detergent fibre (ADF) and 56.5% neutral detergent fibre (NDF) has been reported in the United States (Bitzer et al., 2000).
Table 3. Nutrient profile of kenaf silage in comparison with that of signal grass silage.
Kenaf silage, ensiled in plastic drums1
Kenaf silage, ensiled in plastic drums1
Silawrapped bale Signal grass 2
Age at cutting (in days)/ days ensiled
Both not stated
Dry matter %
Crude Protein %
Crude Fat %
Crude Fibre %
Total Ash %
Total Digestible Nutrient %
Source: 1 Chin et al., ( 2001) 2 Mohd. Najib et al., (1997)
FUTURE PROSPECTS AND RESEARCH NEEDS
Better future prospects for silage use and underlining reasons
Silage use is envisaged to increase in the S.E. Asian region. There are several reasons for this optimism. Stable supply of forage throughout the year is recognised as the key constraint for further development in cattle production in northeast Thailand (Shinoda et al., 1999), and this is generally true for other developing parts of the region. It has been noted that the economic boom of the 1980s and early 1990s have changed the dairy livestock perspective of S. E. Asian farmers and they have become more progressive and farms move from being subsistence to commercialised units (Wong, 1999). Commercial dairy and beef farmers have larger sized herd kept intensively and need greater supply of feed. As the system and scale of production change, the prospect of silage gaining greater importance as one of the feed resource is also enhanced.
There are farmers in the region who have become affluent and their social activities in the community have increased (Hassan Wahab and Devendra, 1982). Likewise, many farmers, especially entrepreneurial producers, have other agricultural or non- agricultural activities. Such situations prevent them devoting too much time to their livestock. Farmers have relied greatly on free family labour to undertake daily chores such as sending animals for grazing, harvesting fodder and/or collection of agricultural crop residues/by-products. However, as countries in the region develop, children of farm families tend to forsake farming. It has been stated that the tedious daily harvesting of green forages throughout the year poses problems for small-scale producers, particularly where family labour is insufficient (Aminah et al., 1999). In such cases, affected farmers are forced into more convenient mode of feeding and silage use is of potential. However, it should be noted that contrary to this, Thai farmers have been observed to lack time and have insufficient family labour for making silage (Poathong and Phakaew, 2001).
Limited availability of land for grazing has already been recognised as one of the major constraints to ruminant production in S. E. Asia (Halim, 1996; Kayouli and Lee, 1999). Rapid development and population growth in countries of S. E. Asia have put pressure on agricultural land use. In many areas, this has deprived livestock of their traditional grazing grounds as well as supply of browses, crop residues and agricultural by-products. Road/highway and local authorities, for instance in Malaysia, do not encourage or allow cattle grazing along roadsides and highway reserves as well as areas in close proximity to township and residential areas. Even for subsistence farmers, with a few animals, harvesting of livestock feed from roadsides and unused agricultural land is becoming less common (Wong, 1999).
An increasing trend towards zero waste agricultural production in some countries of S.E. Asia for environmental protection creates the need to seriously look at converting agricultural wastes into useful material. The pineapple canneries in Malaysia used to discharge much of their waste into rivers, polluting these and the surrounding areas before the enforcement of environmental legislation. As a result of the latter, the large commercial feedlot at Kempas was established to use up the abundant pineapple waste in order to solve the problem of its disposal. Ensilage will be the prospective option for extending the use of such agricultural wastes.
Even with pressure on agricultural land use, there is still an abundance of crop residues and agricultural by-products with potential for ensiling. In Malaysia, besides pineapple wastes and banana rejects, there are another 16 fruit types which are processed and leave by-products with potential to be utilized for feeding (Yu and Chng, 1977, cited by Idris and Birner, 1992). These include guava and passion fruit factory rejects/pulp waste which is being studied for beef fattening. Seasonal surplus of brewer spent grain, currently utilized by some dairy farmers in Malaysia, is hardly exploited and there is the prospect of conserving this through ensiling (Idris and Birner, 1992). In Vietnam, sweet potato (Ipomoea batatas) vines are plentiful although currently used mostly for pigs rather than buffaloes and cattle (Ly, 1996). Anticipating increased cultivation of sweet potato in the future, ensiling of its fresh vines has been suggested as a future prospect since its crude protein of 2.5-3.8% is comparable to the 3.7% of corn stover (Tan, 1999). A hectare of sweetcorn, a popular short-term cash crop in the region, produces an estimated 10 tonnes (Yacob et al., 1992) or 12 tonnes (Idris et al., 1999) of stover dry matter; ensuring abundant supply for ensiling.
The oil palm crop is economically important in Indonesia, Malaysia and Thailand. The oilpalm plantations produce an abundance of pruned fronds every week, which can be exploited as animal feed (Wong 1999). OPF are available either regularly as pruned fronds or every 25 to 30 years, during replanting, as felled fronds. In year 2000 alone, there has been a projected availability of 17.85 and 1.34 million tonnes dry matter from pruned fronds and felled fronds respectively in Malaysia (Abu Hassan and Azizan, 1992). The abundant supply of OPF can be potentially made into silage. In Java, Indonesia, many dairy farmers have shortages of feed in dry seasons yet not far from these areas a great deal of wet rice straw is wasted in the wet season (Ĝrskov, 1998). While pointing this out, it was suggested that, besides use of ammonia as preservative, it may be possible that cellulase enzyme additions can solubilise sufficient cellulose to glucose so that it may be possible to preserve rice straw as silage.
There are prospects for new forage crops being introduced in the future which can produce good quality silage, for example kenaf. This plant is also available in Thailand and Indonesia, although currently grown mainly to produce commercial fiber. Foliage of a variety of mulberry (Morus sp.), analysed to have crude protein of above 30% and apparent digestibility of minimum 80%, is currently being studied at University Putra Malaysia, Serdang, Malaysia, as forage feed, and its conservation as silage will be pursued (Jelan, Z.A., personal communication).
Commercially available silage is a future prospect. It has been stated that farmers may be prepared to buy ready made silage, which indicates willingness to feed it, but lack of time to prepare it (t Mannetje, 1999b). It is reported that the feedlot farm in the Supanburi Province in Thailand purchases each year hay, fresh corn waste, pineapple silage and corn silage amounting to an estimated US$73,000 (Phonbumrung. & Khemsawat, 1998). There are already farmers and entrepreneurs who have made silage into a marketable commodity. In Thailand, three farmers in Pakchong district produce corn silage in plastic bag for sale at 20 kg. silage/bag for 1.50 baht/kg, equivalent to about USD 0.04/kg (Poathong and Phaikaew, 2001). Each farmer can produce and sell 90 tonnes of silage per month to dairy farmers in the district and nearby areas. Likewise, in the sweetcorn stover ensilage project in Trengganu, Malaysia, farmers themselves, forming a co-operative, have taken over from the government to produce and sell silage. An entrepreneur in Malaysia is commercialising OPF silage on a small scale and plans to do the same with corn stover silage.
Potential fields for study and research needs
Limited research is undertaken on silage in S. E. Asia. To cater for the future, more research on ensilage, silage characterisation as well as its usefulness to livestock should be pursued. Suitable ensiling systems should be developed, particularly for smallholders. For a system to be suitable for smallholders in the tropics, it must have low investment costs; be reliable and repeatable; use uncomplicated technology; use locally sourced equipment and consumables; be safe; and give rapid and significant returns on investment (Machin, 1999). The use of bags and containers for ensiling is popular among small farmers and appropriate technology based on these should be further developed.
Work on additives has seen inclusion of molasses, ground maize, palm kernel cake and even poultry litter as substrate or nutrient source to improve feeding value of silage (Chin, 2001). Molasses has increased lactic acid content in grass silage (Aminah et al., 1999) and dry matter losses of both OPF and nepah frond silages during incubation (Abdalla et al., 2001); while urea, added singly and in mixture with molasses, improved ratio of soluble sugar to CP (Abdalla et al., 1998), deemed a possible determinant factor for production of good silage. Besides, substrate or nutrient sources as additives, other generally known categories such as fermentation stimulants, e.g. bacterial inoculants and enzymes, and fermentation inhibitors, such as propionic, formic and sulphuric acids (Woolford, 1984; Henderson, 1993; Bolsen et al., 1995; cited by Titterton and Bareeba, 1999) or as otherwise stated to be biological additives, formic acid and /or formaldehyde treatments (Mühlbach, 1999) should be further studied to improve the silage making process and increase value of silage.
A concern in the ensiling of tropical forages is the low dry matter and water-soluble carbohydrate content, which wilting prior to ensiling can overcome. Production of haylage was successfully studied when foliage from grasses such as napier grass (P. purpureum), guinea grass (P. maximum), koronivia or humidicola grass (B. humidicola) and broadleaf setaria grass (S. sphacelata var. splendida) as well as legumes such as Leucaena leucocephala and Glyricidia sepium were first wilted, under transparent plastic cover, to between 52.8% and 58.1% moisture content over two days before being ensiled (Mohd. Najib et al., 1997). More studies on this will be beneficial, especially for areas of the region where climatic conditions permit. Mechanisation is another field of study, particularly under smallholder systems pertinent to S.E. Asia. For instance, a useful machine (Silager-1) for compacting ensiled material in plastic drum has been developed in Malaysia.
Both expertise and facilities for undertaking research and development (R & D) are currently lacking in S.E. Asia. Consideration should be given to the provision of foreign expertise as well as development of more local expertise. Existing facilities should be improved and new ones established for the same purpose. Funding is an underlining research need. The roles of Farmer Participatory Research (FPR) and Participatory Technology Development (PTD), which are becoming better recognised and accepted with mainstream research, and the participatory extension approaches successfully applied in Laos and Thailand, should be examined for R & D and transfer of the silage technology to farmers in the region (Connell, 2000). This is supported by the fact that the participatory approach to forage technology development used by the Forages for Smallholders Project (FSP) has successfully resulted in greater adoption of forage technologies in Indonesia, Laos, Philippines and Vietnam (Horne et al., 2000).
Silage is not considered of widespread importance in the S.E. Asian region, as most ruminants are still under smallholder farmers who practise a traditional village system of rearing. Ensilaging activities and silage use are still limited and are mainly undertaken by more progressive, specialised and commercial dairy and beef farmers and by pasture-based ruminant ranches or farms. However, prospects for silage use are envisaged to be good for the various reasons discussed. Silage has also become a marketable commodity and some farmers evidently are prepared to buy it ready made. Further research is necessary to support efforts towards greater adoption of silage technology.
The author wishes to express his sincere thanks to the Organising Committee for the XIIIth International Silage Conference for the invitation to present this paper and for sponsoring his attendance at the Conference. He is also indebted to the Director-General of Veterinary Services Malaysia for his full support and permission to present and publish the paper.
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