Genetic variability in a nucleus herd of Boer goats in Brazil assessed by pedigree analysis

Genetic diversity and population structure were analyzed in Boer goats raised in Brazil, based on pedigree information of a population established from 92 animals imported in 1996, which received additional imported embryos in 2000 and some sires from other breeders between 2007 and 2012. Pedigree information on 1826 young kids born between 1997 and 2012 was used in the analyses. The herd census varied considerably among years, with a mean number of registered offspring of 82.1±36.1 kids. The mean generation interval was 3.67±1.81 years, and the mean number of offspring per parent was 19.01±31.38 for sires and 3.85±2.80 for dams. Parents were known for all animals in the reference population (animals born in the period 2009–2012), and 71.4% and 63.5% had grandparents and great-grandparents known, respectively. Animals in the reference population had a mean number of equivalent generations known of 3.55±1.27 years, a mean inbreeding coefficient of 0.75±0.04% and about 19% were inbred. The mean relatedness was 2.28±0.01% for this group of animals. Over the period studied, the rate of inbreeding/year was 0.04±0.0002%, and the effective population size, estimated from the individual rate of inbreeding, was 173.5. The effective number of founders and ancestors represented in the reference population was 33 and 14, respectively, and 15 founders and 5 ancestors contributed with 50% of the gene pool. While in the early years the genetic contributions to the herd were mostly from American-imported animals, in recent years the influence of Brazilian- and Australian-born animals has gained importance. The results of our study indicate that inbreeding has been maintained at low levels in this population, essentially because the herd has been kept open to the introduction of new animals. This strategy should be continued, to maintain high levels of genetic diversity, which are needed for a successful selection program of Boer goats in Brazil.