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Two researches were conducted at the experiment farm of An Giang University, Viet Nam.
The first study on the growth of earthworms (Perionyx excavates) was studied in a 2*2 factorial experiment with 4 replicates, in which the treatments were: source of manure (cow or buffalo) and supplementation with water hyacinth at 25% of the weight of manure (DM basis) or none.
Adding chopped water hyacinth to buffalo or cattle manure led a decrease in worm numbers and in productivity per kg DM and crude protein of added substrate. Relative growth in numbers and in weight of the worms was similar on manure derived from buffaloes and cattle. The negative effect of water hyacinth was greater with buffalo than with cattle manure.
Residual compost from cattle manure was richer in N and poorer in ash than compost derived from buffalo manure. Water hyacinth added to the substrate resulted in compost with less N but more ash.
The second study included two experiments were carried out in the research farm of An Giang University. The first experiment was a study on the growth performance of Marble goby and Tra catfish fed diets of trash fish and rice field prawns replaced (on an iso-nitrogenous basis) with 0, 25, 50, 75 and 100% of frozen earthworms (Perionyx excavates).
The weight gains of Marble goby and Tra catfish, and the survival rate in the Marble Goby, decreased markedly with curvilinear trends as the proportion of frozen earthworms in the diet was increased (Experiment 1). The Tra catfish appeared to adapt better than the Marble goby to the frozen worms. The second experiment, which was designed to test the hypothesis that the poor growth rates with frozen earthworms was due to the low palatability of the earthworms after being frozen, confirmed the negative effects of this method of conservation. Growth rates were 4 and 2 times greater for Marble goby and Tra catfish, respectively, when they were fed fresh rather than frozen earthworms. Survival rate was 100% on the fresh earthworm diet.