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* Centre for Livestock and Agriculture Development (CelAgrid),
Phnom Penh, Cambodia
**Finca Ecológica, UTA-Colombia, AA#48, Socorro, Santander,
Colombia
Eighteen male local “Yellow” cattle with average weight of 101±14.5 kg were allocated in a randomized complete block design (RCB) to a 3*2 factorial combination of 6 treatments, with three replicates of each treatment. The factors were: 3 sources of rumen supplement (water hyacinth leaves, water hyacinth leaves + stem and urea-minerals mixture), and supplementation or not with cassava hay. The basal diet was untreated rice straw fed ad libitum. The rumen supplements were offered at levels to provide 100 g crude protein (CP) per 100 kg live weight. The cassava hay was offered at levels equivalent to 200 g CP per 100 kg live weight.
Live weight gain was increased dramatically when cassava hay was fed. However, there was a significant interaction between the effect of the cassava hay and the rumen supplements. When cassava hay was fed growth rates were higher when the leaves of water hyacinth were given as the rumen supplement with no difference between water hyacinth leaves plus stem and the urea-minerals mixture. In the absence of cassava hay, the cattle fed either leaves or leaves plus stem of water hyacinth lost body weight while those fed the urea-minerals mixture gained in weight. It is concluded: (i) that water hyacinth leaves can be used effectively as a source of rumen nutrients for growing cattle on a basal diet of rice straw provided a source of bypass protein (in this case cassava hay) is also fed; and (ii) that the limiting factors in water hyacinth foliage are the presence of anti-nutritional factors the negative effects of which are exacerbated at low levels of dietary crude protein.