Optimized management of genetic variability in selected pig populations.

Controlling the increase of coancestry and inbreeding coefficients in selected populations is made possible through calculation of the optimal contributions allowed to breeding animals, given the current situation with regard to genetic diversity, and further, through optimal design of matings. The potential of such an approach for pig breeding was tested by retrospective optimization on the French Landrace population in reference to the matings actually carried out during a 21-week test period. The major constraint was that the average overall estimated breeding value (EBV) should be the same as the observed one, for not decreasing short-term genetic gain. Optimizing breeding allocations to boars would have led one to decrease coancestry and inbreeding coefficients by approximately 20%. This decrease would have even increased to approximately 30%, would have replacements and disposals been optimized after accounting for genetic variability, keeping the same constraint of genetic level identical to the observed one. These results showed the potential value, in the future, of completing each periodical calculation of EBVs by optimizations considering genetic variability and of releasing corresponding information to breeders, in order to enhance maintenance of genetic variability.