Dr. Alexander N. Hristov is a Professor of Dairy Nutrition in the Department of Animal Science at The Pennsylvania State University. He earned his Ph.D. in Animal Nutrition from the Bulgarian Academy of Agricultural Sciences and has worked as a Research Scientist in his native Bulgaria, the USDA-ARS Dairy Forage Research Center in Madison, WI, and Ag Canada’s Research Center in Lethbridge, AB. He was Assistant and Associate Professor of Dairy Nutrition with the Department of Animal and Veterinary Science at the University of Idaho in Moscow, ID for 9 years before he came to Penn State in Jan 2008 as an Associate Professor of Dairy Nutrition, and was promoted to Full Professor in 2013.
Dr. Hristov teaches courses in Animal Nutrition and Feed Technology, Advanced Dairy Herd Management, and Ruminology at Penn State. His main field of research is dairy cow nutrition, specifically improving the efficiency of utilization of dietary nutrients for milk synthesis and reducing nutrient losses and gaseous emissions from dairy operations. 
He has served as Division Editor for the Ruminant Nutrition Section of the Journal of Animal Science and Associate Editor for the Canadian Journal of Animal Science. His published works include more than 120 refereed-journal articles, as well as several book chapters. He has also been the editor of two books. Dr. Hristov is a member of the American Dairy Science Association, American Society of Animal Science, Federation of Animal Science Societies, and the American Registry of Professional Animal Scientists. He is also the coordinator of the Network and Database on Feed and Nutrition in Relation to Greenhouse Gas Emissions (FNN), an activity of the Livestock Research Group (LRG) within the Global Research Alliance on Agricultural Greenhouse Gases (GRA) and member of the Feed Composition Committee of the National Animal Nutrition Program (NANP).