Can genetic similarity based on genetic values be used as a mating tool in a Nellore cattle population?

Closed cattle herds face daily the tradeoff between genetic progress speed and long term maintenance of genetic diversity. Using pedigree and genetic merit information coupled with multivariate statistics can yield a mating tool to produce balanced and efficient animals for the traits of interest, minimizing genetic diversity losses. The present study aimed to identify genetically similar groups in a closed herd and explore it as a mating system with minimal reduction in genetic diversity. The database came from a single commercial cattle herd (n = 6,579 individuals with complete information). All statistical analyses were performed using the R software. The principal component analysis was used to verify the relationships between the genetic values for several traits and to choose the variables that would be considered for the grouping according to their genetic similarity. Clustering identified four groups as the best option for this population. The inbreeding rate within clusters was 0.60%, 0.61%, 0.72% and 0.71% for cluster 1, 2, 3 and 4, respectively. Grouping animals according to genetic similarity allows the selection of individuals for the formation of specialized lines. The use of basic statistics can be a simple way of guiding mating in closed herds, which sometimes did not have access to more sophisticated genetic tools as genotyping or mating software.