In-depth pedigree analysis in a large Brazilian Nellore herd.

A large herd of Nellore cattle was evaluated using in-depth pedigree analyses. Taking into account the incomplete pedigree due to the use of multiple young sires for mating, the average inbreeding coefficient was calculated as 1.73% for the last generation, which was higher than the regular inbreeding coefficient (0.25%). The effective population size was estimated to be 114, 245, and 101 for the time periods 1995-1999, 1999-2003, and 2003-2007, respectively. Parameters based on the probability of gene origin were used to describe the genetic diversity over time in the herd. The effective number of founders, ancestors, and founder genomes decreased over time, showing an overall loss of genetic diversity. In the last five-year period (2003-2007), based on available pedigree information, one prominent ancestor contributed 10.6% to the gene pool of the herd, and 30% of this pool was contributed by 31 ancestors. The analysis of inbreeding under random mating indicated that the mating strategies used in the herd are slowing down inbreeding rates. However, it is advisable to continue monitoring the inbreeding rates and genetic diversity in this herd in the future.