Expected progeny differences (EPD) for stayability were estimated for 4,180 sires with daughters in the Program for Genetic Improvement of the Nellore Breed. The univariate threshold sire-maternal grandsire model was used, following a Bayesian methodology. The sires were ranked for stayability in descending order, and those whose EPD were higher than 57.6% were regarded as TOP1%. Pedigree analysis was then conducted in order to establish whether a family tendency was present, as well as the contribution of Nellore founders and ancestors for the trait under consideration. The main founders, which together were responsible for 18.8% of the genes in TOP1% sires, were Karvadi IMP (with 8.2% of genes, basically through its son Chummak), Godhavari IMP (with 6% of genes, through Kurupathy and Neofito), Rastã IMP and Falo da BV (respectively with 2.5% and 2.1%, through mothers, since they are not related to the ancestor sires). Rolex, a polled sire, stayed in twelve lineages - paternal or maternal - through its grandson Cardeal. Among the seven Nellore ancestors with the highest genetic contributions (15.3% of genes when put together), five were of the polled variety. Only 28 animals apportioned 50% of the total genetic variability, which is indicative of the small number of animals used as Nellore reproducers.
beef cattle; Nellore; pedigree analysis; lineages; stayability
