The studies presented in this thesis were conducted at Nong Lam University Experimental Farm,  Ho Chi Minh, Vietnam and was supported by the Swedish International Development Coorperation Agency (SIDA), Department for Research coorperation with Developing countries (SAREC), for which I greatly indebted.

I would like to express my sincerely gratitude to:

Dr. Ngo Van Man and Prof. Dr. Hans Wiktorsson, my supervisors for valuable advice and useful suggestions to me during the implementation the studies.

Prof. Dr. Brian Ogle, Director of “Vietnam-SAREC sustainable Livestock Production Systems” project, for valuable support, especially correction of my English

Prof. Dr. Inger Ledin, Department of Animal Nutrition and Management, SLU for her kind help and encouragement.

Prof. Dr. Luu Trong Hieu, Dr. Nguyen Van Khanh, Dr. Nguyen Nhu Pho, Dr. Duong Duy Dong for their permission, facilitation and encouragement

Mr. Nguyen Van Cong, Dr. Duong Nguyen Khang, Mr. Nguyen Van Hao, Mr. Nguyen Phuc Loc, Mr. Nguyen Quang Thieu, Ms. Tran Thi Phuong Dung, Ms. Nguyen Thi Loc for facilitation and make advantage condition during conducting experiments.

All the lecturers and instructors from the Swedish University of Agricultural Sciences, Sweden; University of New England, Australia; University of Tropical Agriculture, Colombia; KhonKean University, Kasetsart University, Chiang Mai University, Thailand; Namxuang Livestock Research Centre, Northern Agriculture and Forestry Research Centre, Laos; Centre for Livestock an Agriculture Development, Cambodia; An Giang University, Can Tho University, Nong Lam University, Hue Agriculture and Forestry University, Vietnam for their expert knowlegement and contributions into the our courses.

My undergraduate students Mr. Dinh Cong Tien, Mr. Nguyen Ngoc Tuan, Mr. Ho Van Thinh for help in taking care the experiments.

My friends Daovy, Khamparn, Malavanh, Latsamy, Ammaly, Keosath, Buntha, Sokha, Phiny, Nem, Joe, Too, Ngoc, Hue, Nha, Tham, Thao for keeping a warm atmosphere and valuable help during the time away home.

To my family, my respectable mother and father, my older sisters, my younger brothers for all the encouragement and helping during the studying.

The last, my gratitude to all those anonymous peoples who the names can not appeared in here.