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This paper presents a descriptive and evaluative analysis of the productive and environmental of SPSi with Leucaena leucocephala (Lam.) de Wit, emphasizing the nutritional quality, biomass production, voluntary intake, animal productivity and greenhouse gas emission aspects. For such purpose, a bibliographic review was made about the studies in the last 15 years, concerning animal production systems under tropical conditions, stressing the ones conducted in Colombia. It was noticed that the forage offer in SPSi with leucaena has a protein content higher than 22 % and a lower fiber content (20-30 %) with regards to most tropical pastures. Additionally, leucaena has the capacity to withstand intense browsing, and its presence increases plant and animal productivity. The animals produce at least two or three times more meat and milk ha-1 year-1 as the result of a higher nutrient intake and higher forage offer, because with this legume the dry matter (DM) intake can be 1,3 times higher than the one observed in conventional systems, and the forage production can be from 5 to 18 t DM ha-1. On the other hand, the inclusion of L. leucocephala allows to decrease the enteric emissions of CH4 in amounts close to 20 % per kilogram of produced meat or milk and per kilogram of consumed dry matter. Compared with the traditional systems, in the ones in which L. leucocephala is included, the efficiency in production is increased and the negative environmental effects of animal husbandry are decreased. [ABSTRACT FROM AUTHOR]

The objective of this analysis is to reflect on more sustainable family and extensive integrated livestock production models, in which the woody component is integrated, contributing to the reduction of greenhouse gases and favoring the mitigation of the climate change. For such purpose, a revision was made referring to the integration of the forestry activity in livestock production, as a viable alternative of production system. A start is made from the criterion that silvopastoral systems (SPSs), within the agroforestry ones, are agroecosystems in which a tree component is associated with a herbaceous (natural or improved pastures) and a farming component (livestock) in the same site, where biological interactions exist among them and land use is maximized. This paper also describes how SPSs are grouped; their opportunities from the economic, productive, social and environmental points of view; and the effects of the interaction among its components. This analysis allows to state that SPSs are a product of the relation among biology, society and culture, and in them there is a large diversity; likewise, they allow the reconversion of the very little productive extensive livestock production into more productive and sustainable systems, as well as the rehabilitation of the areas degraded by this type of livestock production, deforestation and soil depletion. [ABSTRACT FROM AUTHOR]