Minimizing Inbreeding by Managing Genetic Contributions Across Generations

Corresponding author: Leopoldo Sánchez, Centre de Recherches d'Orléans, Avenue de la Pomme de Pin, B.P. 20619 Ardon, 45166 Olivet Cedex, France., leopoldo.sanchez{at}orleans.inra.fr (E-mail)

Communicating editor: J. B. WALSH

Here we present the strategy that achieves the lowest possible rate of inbreeding (F) for a population with unequal numbers of sires and dams with random mating. This new strategy results in a F as much as 10% lower than previously achieved. A simple and efficient approach to reducing inbreeding in small populations with sexes of unequal census number is to impose a breeding structure where parental success is controlled in each generation. This approach led to the development of strategies for selecting replacements each generation that were based upon parentage, e.g., a son replacing its sire. This study extends these strategies to a multigeneration round robin scheme where genetic contributions of ancestors to descendants are managed to remove all uncertainties about breeding roles over generations; i.e., male descendants are distributed as equally as possible among dams. In doing so, the sampling variance of genetic contributions within each breeding category is eliminated and consequently F is minimized. Using the concept of long-term genetic contributions, the asymptotic F of the new strategy for random mating, M sires and d dams per sire, is /(12M), where = [1 + 2(¹/₄)^d]. Predictions were validated using Monte Carlo simulations. The scheme was shown to achieve the lowest possible F using pedigree alone and showed that further reductions in F below that obtained from random mating arise from preferential mating of relatives and not from their avoidance.

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