HUE UNIVERSITY HUE UNIVERSITY OF AGRICULTURE AND FORESTRY BOUNTHAVY VONGKHAMCHANH USES OF BIOCHAR AND CASSAVA FOR CATTLE PRODUCTION AND METHANE REDUCTION IN LAO PDR DOCTOR OF PHILOSOPHY IN ANIMAL SCIENCES HUE, 2021 HUE UNIVERSITY HUE UNIVERSITY OF AGRICULTURE AND FORESTRY BOUNTHAVY VONGKHAMCHANH USES OF BIOCHAR AND CASSAVA FOR CATTLE PRODUCTION AND METHANE REDUCTION IN LAO PDR SPECIALIZATION: ANIMAL SCIENCES CODE: 9620105 DOCTOR OF PHILOSOPHY IN ANIMAL SCIENCES SUPERVISORS: 1: ASSOC PROF DR LE VAN AN 2: DR DUONG THANH HAI HUE, 2021 GUARANTEE I hereby guarantee that scientific work in this thesis is mine All results described in this thesis are righteous and objective They have been published in the journal of Champasak Province, Lao PDR, journal of Livestock Research for Rural Development (LRRD), JASTD, Lao PDR, and Journal of Animal Husbandry Sciences and Technics (JAHST), Vietnam Hue University, 2020 Bounthavy, PhD student DEDICATION To my parents, my wife (Sangsavanh Niemthachit), daughter (Sangmany Vongkhamchanh) and son (Pharkdy Vongkhamchanh) i ACKNOWLEDGEMENTS I would like to express my sincere gratitude and appreciation to my major advisor, Assoc Prof Le Van An, Department of Animal Husbandry, Fuculty of Animal Husbandry and Veterinary Medicine, University of Agriculture and Forestry, Hue University for his precious advice, guidance on thesis, encouragement, and constructive comments My deeply grateful and sincere gratitude is extended to my co-advisor, Duong Thanh Hai, Ph.D., Department of Animal Husbandry, Fuculty of Animal Husbandry and Veterinary Medicine, University of Agriculture and Forestry, Hue University for his kindness in advising research proposal and experiment I am grateful to all professors, teachers, and staff of the Faculty of Animal Husbandry and Veterinary Medicine for the suggestion, which enables me to complete my work I would like to thanks MEKARN II project and Hue University of Agriculture and Forestry for providing the financial support for my study that enables me to complete this study Finally, I am grateful to my family for their financial support, care, and love I would like to express my deep gratitude to Professor Thomas Reg Preston, for guiding the experiments during the study and helping me to author my journal I would also like to extend sincere thanks to several people who facilitate, encourage, and support the whole Ph.D course such as Professor Dr Ewadle, International Coordinator MEKARN II project; Dr Vanthong Phengvichith, National Agriculture and Forestry Research Institute (NAFRI), Dr Daovy Kongmanila, National Univerisity of Lao PDR; Dr Kieu Borin, MEKARN II regional coordinator; Dr Ngo Tung Duc, the Head of Education Department, Hue University of Agriculture and Forestry Warm thanks are extended to my Ph.D classmates from the three countries: Laos, Vietnam, and Cambodia, for sharing the culture, friendship, and creating a warm atmosphere throughout the Ph.D course ii ABSTRACTS Cattle are regarded as one ruminant of livestock that is expressed the importance for smallholder and account are more than 50% of cash income in Laos However, barriers to cattle production are mainly limitation of feed qualities and quantities, and methane emission by enteric fermentation where consider as one source of greenhouse gases Therefore, these studies aimed to evaluate the utilization of cassava supplied by biochar to mitigate methane production in an In vitro rumen incubation and incorporated with the diets for fattening local yellow cattle Chapter (experiment 1) The rice straw and cassava leaf meal were used as substrate Urea was used as a source of NPN and protein Gas production and methane in the gas were measured over successive h intervals for 24 h, after which the residual dry matter (DM) in the substrate was determined by filtration During the fermentation intervals (18 – 24 h) there were significant differences in gas production between two substrates, rice straw (276.67 ml) and cassava leaf meal (515 ml) (p