The livestock sector is transforming rapidly in response to shifts in the global economy and changing societal expectations. Society expects the livestock sector to provide safe and plentiful food and fibre for growing urban populations, livelihoods for more than a billion poor producers and traders as well as global public goods related to food security, environmental sustainability and animal-borne diseases. But the rapid pace of change has led to unbalanced growth of the sector. This has manifested itself in a widening dichotomy within the sector in terms of the scale, intensity and efficiency of production and in unforeseen social, nutritional, animal health and environmental implications. These changes and the speed with which they are occurring have created systemic risks for livelihoods, human and animal health and the environment. To meet the challenges and constraints of the 21st century, the livestock sector requires appropriate institutions, research, development interventions and governance that reflect the diversity within the sector and the multiple demands placed upon it. Also published in Arabic, English, French, Russian and Spanish.