ORIGINAL RESEARCH Significant mortality of large ruminants due to hypothermia in northern and central Lao PDR Syseng Khounsy & Sonevilay Nampanya & Phout Inthavong & Moua Yang & Bounkhoung Khamboungheung & Michaela Avery & Russell Bush & Luzia Rast & Peter A. Windsor Accepted: 30 August 2011 /Published online: 8 September 2011 # Springer Science+Business Media B.V. 2011 Abstract An extreme cold exposure event occurred be- tween March 14th and 19th 2011 in northern and central Lao PDR resulting in a major mortality of cattle and buffalo. At least six northern and one central province reported losses, involving 46 districts and 1,384 smallholder farmers, with a total of 7,162 cattle and 3,744 buffalo reported to have died in association with cold weather. Affected animals were observed to shiver, display slow and shallow respiration, lose consciousness and eventually die. Many deaths occurred at night and were recorded in both sexes and all ages of large ruminants. However, mortalities occurred mostly in animals that were free-grazing in the forest and natural grassland, and exposed to the cold weather. Some housed animals that were provided with warmth from shelter and fires and supplementary feed did not die. Samples from dead animals collected for laboratory analysis confirmed that bacterial or viral pathogens were not present. The cause of the mortality was attributed to hypothermia, and the economic losses were estimated at USD 2,463,912.00. Xieng Khouang Province reported the most severe losses with deaths of 4,600 cattle and 1,665 buffalo. At Thong Haihin meteorological station in this province on March 16th and 17th 2011, minimum temperatures recorded were 6.7°C and 7.5°C and rainfall recorded was 36.6 mm and 61.7 mm, respectively. This was the first reported extreme cold event in living memory occurring between the end of dry season and beginning of the wet season in northern Laos. This event is reported in detail as it caused a major loss of wealth for poor smallholder farmers and indicates that strategies to minimise the impact of extreme cold weather events need to be included in livestock development extension programmes. Keywords Cattle and buffalo . Exposure . Climate extreme . Thermal stress . Lao PDR . Hypothermia Abbreviations ACIAR Australian Centre for International Agricultural Research ADB Asian Development Bank DLF Department of Livestock and Fisheries DoS Department of Statistics Lao PDR Lao People’ s Democratic Republic Introduction The Lao People’ s Democratic Republic (Lao PDR) is a landlocked country located in the heart of South East Asia, with a population of 6.83 million in 2009 and a land area of 236,800 km 2 (Department of Statistics DoS 2005). It is recognised as a poor country with 73% of the population living in rural areas and 74% of these people living on USD 2 per day (World Bank 2007). Livestock production is an important livelihood activity of smallholder farmers in Lao PDR with sales of livestock contributing up to 50% of annual cash income for many upland farmers (Asian Development Bank ADB 2005; Stür et al. 2002). More than 95% of all livestock is owned by smallholders who rely on fewer than five head of cattle and buffalo per S. Khounsy : P. Inthavong : M. Yang : B. Khamboungheung Department of Livestock and Fisheries, Ministry of Agriculture and Forestry, Vientiane, Lao People’ s Democratic Republic S. Nampanya : M. Avery : R. Bush : L. Rast : P. A. Windsor (*) Faculty of Veterinary Science, University of Sydney, Camden, NSW, Australia e-mail: peter.windsor@sydney.edu.au Trop Anim Health Prod (2012) 44:835–842 DOI 10.1007/s11250-011-9975-1