Evolution de la diversité génétique des populations françaises de bovins allaitants spécialisés de 1979 à 2008

Abstract

This paper presents an analysis of the genetic variability of the three main beef cattle breeds in France using pedigree analyses. In the three breeds, two breeder nuclei are influent on other herds of the population with on-farm performance recording because they provide numerous natural service bulls or young males for artificial insemination (AI) in breeding programs. The degree of pedigree knowledge is good but heterogeneous between breeders and producers. Estimated levels and rates of inbreeding are low to moderate (0.01%, 0.1% and 0.20% per generation for the Limousin, Charolais and Blonde d'Aquitaine populations, respectively). They correspond to large genetic effective sizes (>1000, 601 and 247 in the Limousin, Charolais and Blonde d'Aquitaine breeds, respectively) and therefore to important genetic variability. Effective sizes estimated for breeder nuclei are lower than those estimated for other production herds with performance recording but are nevertheless large. The evolution of the statistics derived from probabilities of gene origin shows occurrence of old bottlenecks in the Blonde d'Aquitaine population resulting from a large AI use in the past. In the Charolais and Limousin breeds, bottlenecks are more recent and result from a low but increasing AI use. To preserve genetic variability, it would be advisable to balance contributions of each bull to the cohort of males recruited for the breeding program for insemination bulls and to maintain a minimal proportion of natural service sires of son.