Improved efficiency in the use of natural resources, pragmatic production systems and environmental sustainability, justified by the need for improved land use systems and increased productivity, are discussed in the context of Asian integrated systems, diversification, and issues of sustainability. The importance of these are reflected by serious inadequate animal protein production throughout Asia, where available supplies cannot match current and projected human requirements up to 2050. Among the ruminant production systems, integrated tree crops-ruminant production systems are grossly underestimated and merit emphasis and expansion. As an example, integrated oil palm- based system is an important pathway for integration with ruminants (buffaloes, cattle, goats and sheep), and provides the entry point for development. The importance and benefits of integrated systems are discussed, involving animals with annual and perennial tree crops, integration with aquaculture, the significance of crop-animal interactions, stratification of the systems, production options, improved use of forages and legumes, potential for enhanced productivity, implications for improved livelihoods of the rural poor and the stability of farm households. The advances in research and development in South East Asia highlight demonstrable increased productivity from animals and meat offtakes, value addition to the oil palm crop, sustainable development, and distinct economic impacts. The results from 12 out of a total of 24 case studies concerning oil palm over the past three decades showed increased yield of 0.49-3.52 mt of fresh fruit bunches (FFB)/ha/yr; increased income by about 30%; savings in weeding costs by 47- 60% equivalent to 21-62 RM/ha/yr; and an internal rate of return of 19% based on actual field data. The results provide important socio-economic benefits for resource-poor small farmers. Potential increased offtakes and additional income exist with the integration of goats. Additionally, the potential for carbon sequestration with tree crops is an advantage. The reasons for low adoption of the syatems are poor awareness of the potential of integrated systems, resistance by the crop- oriented plantation sector, and inadequate technology application. Promoting wider expansion and adoption of the systems in the future is linked directly with coherent policy, institutional commitment, increased investments, private sector involvement, and a stimulus package of incentives.