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.
Scope for selecting many breeding stocks of possible economic value in the future
Current animal improvement deals largely with selection of stocks for current economic objectives. However, there is uncertainty about how well these objectives will hold in the future, since husbandry and marketing needs and conditions may change unpredictably over time. The scope for developing alternative stocks, selected for different chosen sets of objectives, is considered, so that by substitution or crossing it may be possible to reduce the uncertainty and better meet future needs and conditions. The reduction in uncertainty is modelled by including risk or uncertainty in the discount rate in assessing benefits over time from one cycle of selection. From the national viewpoint, the costs of developing alternative selection stocks are small relative to the possible returns. Thus, if the uncertainties were reduced by having them, a large number of such alternative stocks would be justified. The expected benefits to the community from animal breeding would also be increased thereby.
Cost-benefit analysis
It was stressed in earlier chapters that planning is a multi-level process. The broad strategy of planning has necessarily to be worked out at the macro level. Within the pattern set by this strategy, consistent growth for different sectors has to be ensured: this is where input-output analysis is useful. But the achievement of sectoral targets in turn requires the efficient planning of individual projects within each sector. Techniques of project appraisal such as cost-benefit analysis are directly concerned with the third level, i.e. microplanning. However, a meaningful interaction with higher levels of planning is crucial to their success. Hence cost-benefit analysis must always be viewed in the broader perspective of planning for development.