Provides a brief outline of the theory and practice of livestock systems research, and presents the fruits of both ILCA's own long experience of livestock systems research and of expertise and efforts of others in the field.

Presents and discusses research results on feed resources, agroindustrial by-products utilisation, forage production, use of crop residues, dairy feeding systems, feeding strategies, introduction and adoption of improved forage technologies, nutritive value of different forages, effects of management on animal performance, effect of supplements on feed utilisation, potential of agricultural by-

Unasylva examina el significado de los bosques para la seguridad alimentaria, formulando la siguiente pregunta: Cmo hacer que los programas y actividades de desarrollo forestal sirvan para asegurar econmica y materialmente a todo el mundo, en todo momento, el acceso a su alimento? En el artculo de fondo M.

Le prsent numro d'Unasylva examine en dtail le rapport entre la foresterie et la scurit alimentaire et se pose la question suivante: Que peut-on faire pour que les programmes et activits de dveloppement forestier contribuent dans la mesure du possible assurer l'accs conomique et physique aux produits alimentaires pour tous et en tout temps? Dans l'article de fond, M.

The current issue of Unasylva takes a long look at the relationship of forestry with food security, and asks the question, ''How can forestry development programmes and activities become as relevant as possible in ensuring economic and physical access to food by all people at all times?" In the lead article, M.

Ever since colonial administrators and western trained scientists became involved in sub-Saharan Africa in the early 20th century and were faced with the task of governing countries where livestock production was a major economic enterprise, the proper utilisation of rangelands became a major concern.

This article suggests that communual rangeland management policies in Botswana and Zimbabwe are based on incorrect technical assumptions about the stability of semiarid rangelands, the nature of rangeland degradation, and the benefits of destocking.

In their recent paper, de Leeuw and Tothill (1990) discussed the shortcomings of estimating carrying capacity (CC) of pastoral systems in Africa. They noted the difficulty of determining available forage per animal due to high annual and spatial variability in plant production, seasonal changes in forage quantity and quality, livestock species mix, and the use of supplemental feeds.

This document contains a collection of critical comments by experts working in the field of pastoralism with regard to several PDN papers.