Effect of earthworms as replacement for trash fish and rice field prawns on growth and survival rate of marble goby (Oxyeleotris marmoratus) and Tra catfish (Pangasius hypophthalmus)Nguyen Huu Yen Nhi, T R Preston*, Brian Ogle** and Torbjorn Lundh**
An Giang University, 25 Vo Thi Sau St., Long Xuyen City, Vietnam
* TOSOLY, AA 48 Socorro, Colombia.
** Department of Animal Nutrition and Management, Swedish University of Agricultural Sciences,
P.O. Box 7024, 750 07, Uppsala, Sweden.
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.