Acknowledgements

The studies presented in this thesis were conducted at the experimental farm of the Aquaculture Department, Agriculture and Natural Resources Faculty, An Giang University, Vietnam, supported by the Swedish International Development Agency/Department for Research Cooperation with Developing countries (SIDA/SAREC) through the regional MEKARN project.

I would like to express my sincere gratitude to:

The Department of Animal Nutrition and Management, Swedish University of Agricultural Sciences for helping to organize and administer the MSc. Program “Tropical Livestock Systems”.

Prof. Dr. Brian Ogle and Associate Prof. Dr. Torbjorn Lundh, Department of Animal Nutrition and Management, Swedish University of Agricultural Sciences, my supervisors, for valuable advice and useful guidance during the study period.

Dr T R Preston, TOSOLY, UTA-Colombia, AA#48, Socorro, Santander, Colombia, my supervisors ,for his kind help in processing the data and encouragement, useful guidance to me during my study and his reading, correcting and follow-up of this thesis to full completion

Dr. Ngo Van Man, the Regional Coordinator of MEKARN for the arrangements of the course and Mr. Nguyen Van Cong for his valuable support.

 All the professors, doctors, lecturers and instructors from the Swedish University of Agricultural Sciences, Sweden; University of New England, Australia; Center for Livestock and Agriculture Development (CelAgrid), Kampong Cham National School of Agriculture, Cambodia; Champasack University, Souphanouvong University, Lao PRD; An Giang University (AGU), Can Tho University (CTU), and Nong Lam University (NLU), Vietnam for transmitting their wide knowledge to our courses.

The Binh Thanh hatchery in Chau Thanh district, An Giang province for their supply of the fry fish to my experiment.

My colleagues and the staff in the laboratory for creating favorable conditions and sharing their practical experience in scientific research.

My students who help me collect the earthworms, trash fish, and rice field prawn, water hyacinth, and who helped in the conduct and care of the experiment.

My friends Giang, Phuong, Tuan, Sorphea, Sophea, Sarouen, Sophal, Lotchana, Bounthavone for creating the open atmosphere and their valuable help during the time away from home.

To my family, my respectable parents, my older brothers, my older sisters, my younger sister and my intended husband for sharing weal and woe in hard times, their belief in me as well as the encouragement to me during the period of study.