A network model that determines the optimal path of breed-crossing decisions to maximize net returns☆
Abstract A model for finding the sequence of breed-crossing decisions that maximizes the expected discounted net returns over a given number of generations is presented. The method is based on network analysis. The assumptions are that there is an initial breed of females, and that all females, in a generation will be mated to one of a given number of alternative breeds. The optimal path of breed-crossing decisions depends on the revenues expected from additive direct effects, maternal effects. breed-specific individual and maternal heterosis effects, and the cost associated with choosing a particular breed of sires. A simple numerical example is presented.
Indicators and framework for analysing the technical and economic performance of irrigation systems at farm level
In North African countries, irrigation considerably increases production. Given the run‐down condition of irrigation equipment, the rehabilitation and modernization of irrigation schemes is a topical question. In addition, some irrigation projects are currently being implemented thus requiring investments, and judicious decisions have to be taken. At the same time farms in North Africa are increasingly confronted with environmental constraints and held accountable for environmental practices. This article proposes an approach to simultaneously take into account the technical, agricultural, economic and environmental objectives at the farm level, considered to be a relevant decision unit. Such indicators enable pertinent comparisons of different water management strategies in private, public and mixed systems. A method is proposed for the calculation of performance indicators from the plot to the farm level. The indicators enable the performance of irrigated systems to be compared in terms of both effectiveness and efficiency. A graphic representation of the indicators enables the synthetic analysis of the results for a given farm thereby making it possible to highlight the weakness of the production system. The method is applied to two farms in the Gharb area in Morocco and two farms in the Mitidja plain in Algeria. Copyright © 2009 John Wiley & Sons, Ltd.
An alternative philosophy for livestock breeding
Abstract The merits of animal breeding are related to the rate of improvement which can be offered. Objectives however may alter particularly as a result of social change, so that improved local livestock may be left adapted to outdated conditions, thus emphasising the need for flexibility. Historically such flexibility and indeed much improvement has depended on the introduction of superior strains, previously selected by others, which happened to meet local requirements. The development of strains with divergent biological characteristics as a supplement to existing policies would increase genetic flexibility, could facilitate a faster genetic response and aid the rapid improvement of indigenous breeds. Such a policy would ensure the availability of appropriate genetic variation in the future and thus provide a positive complement to the passive conservation of “rare” breeds.