Livestock are very important for the livelihood of the majority of people in developing countries, and also as a source of renewable energy for draft purposes and as a source of organic fertilizer for their crops (Steinfeld 2006).
Cambodian farmers, like those in other developing countries in SE Asia; have various sources of livelihood, which range from rice farming, vegetable and fruit cultivation in home gardens, other non-rice crop cultivation in upland areas, animal husbandry and fishing (Yang Saing Koma 2001). In the farming system, livestock play a crucial function. Cattle and buffaloes provide most of the draught power and the manure is used to fertilize crops in the system. Moreover, they are an important social asset and prestige for the rural farmers.
The total number of cattle and buffaloes in Cambodia was reported to be around 3 million and 0.7 million, respectively (MAFF 2004). The number of cattle has fluctuated while buffaloes have declined slightly during the period 1994-2004. The feeding of cattle and buffaloes mainly relies on grazing on common areas but at present this has been significantly declining. Among the constraints for their development appears to be a lack of fodder supply, particularly in the dry season, which affects the performance and the production of cattle and buffalo. Due to shortage of grazing, rice straw plays an important role as a feed source albeit of low nutritional value. In the rainy season, the feed supply remains poor because the grazing area used in the dry season is needed for rice production. As a result of poor management, community land is heavily overgrazed and degraded (Yang Saing Koma 2001).
Poor-quality feed and fluctuating feed supplies are the biggest constraints to increasing livestock productivity in many tropical countries (ILRI 2009). In order to improve this situation, there is a need to look at ways for extending the availability and quality of the available feed resources.
Water hyacinth (Eicahronia crassipes) is a water plant that can be collected locally from rivers, lakes and ponds in Cambodia, as in other tropical countries. It is one of the fastest growing plants, which is known to double its biomass in two weeks (Upadhyay et al 2007). The plant impacts dramatically on water flow, blocks sunlight from reaching native aquatic plants, starves the water of oxygen, and often kills fish. Based on these reasons, it has been recommended that water hyacinths should be removed from water surfaces to limit the disadvantages attributed to this plant (Skinner 2007). This process would be facilitated if it could be used as a feed for animals.
Utilization of water hyacinth as an animal feed has been reported by Hentges (1970), Salveson (1971) and Stephens (1972). When land forages were limited, cattle have been noticed grazing floating water hyacinths (Little 1968). Hentges (1970) reported that the amount of water hyacinth voluntarily consumed by cattle was less than the requirement for maintenance. In order for water hyacinth to be fed as the basis of the diet it therefore needs to be complemented with other nutrient-rich feeds. Water hyacinth foliage is rich in protein and minerals (Abdelhamid and Gabr 1991), thus the other approach to the use of this plant is to consider it as a rumen supplement to complement crop residues such as rice straw which are deficient in such nutrients. For this purpose it needs to supply readily fermentable nitrogen and minerals as well the “unknown” factors often associated with green feeds (Preston and Leng 2009). However, even when the needs of rumen micro-organisms are met, basal diets such as rice straw must also be supplemented with sources of “bypass” or “escape” protein (Preston and Leng 2009) in order to meet the requirements for production. In this respect cassava foliage has proved to be a valuable supplement in diets that otherwise supply only “rumen” nutrients (Ffoulkes and Preston 1978). These authors showed that fresh cassava foliage supported the same growth rate as soybean meal for fattening cattle fed a basal diet of minerals-urea. On diets of rice straw fed to growing cattle, rates of live weight gain were increased by supplements of fresh cassava foliage (Seng Mom et al 2001), cassava leaf meal (Ho Thanh Tham 2008) and sun-dried cassava hay (Keo Sath et al 2007).
For the above reasons it was decided to evaluate the potential advantages of combining fresh water hyacinth and sun-dried cassava foliage (hay) as respective sources of rumen nutrients and bypass protein in a basal diet of rice straw fed to growing cattle of the local “Yellow” breed.
The hypotheses to be tested were:
· Giving water hyacinth foliage as a supplement to rice straw fed to local “Yellow” cattle will have a similar effect as a “rumen” supplement containing urea, minerals and minerals
· Water hyacinth leaves will have a better feeding value than the whole aerial part containing stems as well as leaves
· Cassava hay will supply bypass protein and there fore, because all diets are devoid of bypass protein, will enhance performance on all the diets