Pedigree analyses in the Breeding Program for Nellore Cattle

ABSTRACT. Parameters based on the probability of gene origin were used to describe genetic variability in three reproductive groups from the Breed-ing Program for Nellore Cattle (PMGRN). The three reproductive popula-tions (cows in reproductive age, bulls from artificial insemination centers and young bulls in progeny test) generated medium to low values. The ef-fective number of founders (Nf), the effective number of ancestors (Na) and the remaining genomes (Ng) suggest low founder representativeness, high genetic contribution by some ancestors, considerable loss of founder alleles and lack of allelic representativeness in bulls kept in artificial insemination centers and young sires in progeny test in relation to the diversity on the farms participating in the PMGRN. The parameters based on the probabil-ity of gene origin in the three reproductive groups were: 84.3, 53 and 54.2 (Nf); 71, 36.6 and 30 (Na) and 51.4, 19.3 and 19 (Ng) for cows, bulls from artificial insemination centers and young sires in progeny test, respectively. Future matings and the introduction of selected progeny reproduction may decrease the parameters based on the probability of gene origin in each re-productive group, thereby increasing considerably the additive relationship in the three reproductive groups and consequently increasing the probabil-Genetics and Molecular Research 6 (4): 1044-1050 (2007) www.funpecrp.com.br 1045Pedigree analyses in the Breeding Program for Nellore Cattle ity of inbreeding in the future. Strategies to maintain genetic variability in bull populations must be implemented