Optimised management of genetic variability in selected pig populations : the example of the French Landrace collective population

Abstract

Tempering the increase of coancestry and inbreeding coefficients in selected populations is made possible through calculation of the optimal contributions allowed for breeding animals, given the current situation with regards to genetic diversity, and furthermore, through optimal distribution of matings. The potential of such an approach was tested by retrospective optimisation on the French Landrace po-pulation in reference to the matings actually carried out during a 21-week test period. The major constraint was that the average overall EBV (Estimated Breeding Value) should be the same as the observed one, in order to not damage short-term genetic gain. Optimising breeding allocations to boars would have led one to decrease coancestry and inbreeding coefficients by about 20 %. This decrease would have even climbed to about 30 %, if replacements and disposals had been optimised after accounting for genetic variability while keeping the same constraint of genetic level identical to the observed one. This last optimisation gave the appropriate information fordefining a penalized overall EBV for each individual, combining the current EBV and a penalty proportional to this coancestry with the rest of the population. Weight of coancestry was found to be very high, despite the strong requirement of maintaining the same genetic level for the current overall EBV. These results show the potential value, in the future, of completing each periodical calculation of EBV by optimisations considering genetic variability and of releasing the corresponding information to breeders, in order to enhance maintenance of genetic variability.