III

ACKNOWLEDGEMENTS

I would like to express my deepest respect and most sincere gratitude to my supervisor, Prof. Dr. K. J. Peters, for his guidance and encouragement at all stages of my work. His constructive criticism and comments from the initial conception to the end of this work is highly appreciated. I am greatly indebted to his assistance and understanding in matters of non academic concern which have helped me endure some difficult times during my study period.

I am thankful to Prof. Dr. G. Seeland for willingly accepting to evaluate my Thesis and sit in the examination committee. I thank Dr. T. Hardge and Dr C. Kjora who were members of the examination committee and Prof. Dr. K. Hagedorn for willingly accepting to chair the committee.

I am very grateful to the International Livestock research Institute (ILRI) formerly ILCA, International Livestock Centre for Africa, for providing me the experimental animals and for allowing me to use its computer, library and laboratory facilities. My most sincere thanks and appreciation are also due to the staff of ILRI's experiment station at Debre Birhan for managing the experimental flock and for their tireless assistance in the data collection process. My heart felt thanks also go to the staff of the animal nutrition laboratory of ILRI in Addis Ababa for their kind assistance in analytical work.

My deep gratitude also goes to Dr. Ed Rege for his guidance and assistance as co-supervisor and for allowing his staff to help in the data collection and compilation.

My thanks and appreciation also go to the German Academic Exchange Service (DAAD) for giving me the scholarship which enabled me to undertake this study. The financial support I received from Humboldt University of Berlin at the latter part of my study is also highly appreciated. I am very grateful to Dr. Ursula Grawert of the International Students Office of Humboldt University for her kind consideration and support.

I am also deeply indebted to Dr. Ulrike Funke and Mr. Christian Funke for their constant encouragement and support throughout. Without their unreserved support completion of this work would not have been possible.

The support and encouragement I received from Dr. C. Kijora is highly appreciated. I would like to express my gratitude to Dr. Birgit Zumbach not only for her constant encouragement but also for reading and editing the manuscript, for her help in translating the summary to German and in the preparation of the transparencies required for the defence. My sincere thanks also go to Mrs. Friedlieb and Mr. Seekamp of the Faculty's computer centre in Dahlem for their help in data management.

IV

My deep appreciation also goes to Dr. Getaneh Bitew and his wife Yeshifana Genet, Dr. Melesse Agegnehu, his wife Aberash Wolansa and their daughter Tsellot, Br. Seifu and his wife Misrak and all the other brothers and sisters at the Bethelehem church, who are many to name here, for their love and hospitality I received throughout. May GOD bless them all.

I also wish to express my heart felt thanks to Mr. Günther Fuhr for his unreserved help and services he gave not only for me but also to my friends and colleagues. My thanks also go to all my friends in Berlin, who are many to name here, for their support and encouragement.

I am also very grateful to all my friends and colleagues in Ethiopia, who have supported my wife and our children in many ways during my absence and made it possible for them to endure the loneliness they had for so long. My thanks specially go to Dr. Alemu G. Wold and his family, Mr. Tesfaye Zegeye and his family, Mr. Daniel Mamo and his family, Dr. Zinash Sileshi and her family, Mr. Siraj and his family, Mrs. Birhane Worku and her husband Mr. Tadesse, Mrs. Roman Venchezo and her family, Dr. Girma Abebe and his family and all the others who are many to name here for supporting my family while I am away.

A very special appreciation is due to my wife Etabezahu Eshetu not only for her constant encouragement but also for her patience and understanding throughout. May GOD bless her in all her endeavours because without her unreserved support, completion of this study would not have been possible. I am also greatly indebted to our son Henok and our daughters Mahlet and Bezaye for enduring my absence for so long and giving me their love and encouragement throughout.

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