Driven by population growth,urbanization, and increased income, the demand foranimal-source food products in developing countries israpidly increasing. Livestock, which already constitutes 30percent of the agricultural Gross Domestic Product (GDP) inthe developing world, and about 40 percent of the globalagricultural GDP, is one of the fastest-growing subsectorsin agriculture. Growing demand presents real opportunitiesfor economic growth and poverty reduction in rural areas. Itcould directly benefit the one billion poor people whodepend on livestock as a source of income and subsistence.Livestock also provides traction for about 50 percent of theworld's farmers and is a source of organic fertilizerfor most of the world's croplands, converting wasteproducts into inputs in the production of high-value food.For these reasons, the sector has a critical role to play inmaking agriculture sustainable, in reducing poverty, and incontributing to economic growth. This report presents ananalysis of the issues related to market failures in thelivestock sector, and an examination of policy andinvestment options that can be used to overcome them. Itsprincipal intended audience includes policy makers anddevelopment practitioners. Much of the analysis will focuson identifying the needs of the public sector as it sets outto redress the imbalance between public and privateinvestment and to begin establishing an enabling environmentin which private sector livestock development can take placein a way that is consistent with public health, povertyreduction, and environmental sustainability. While thereport focuses on developing countries, much of itstreatment pertains to industrialized countries as well,particularly with respect to issues of crosscutting globalsignificance, such as greenhouse gas emissions and emerginghighly infectious diseases.