This study aimed to investigate the genetic diversity, population structure,
addition to the effects of inbreeding on the growth characteristics of the breed Nelore
created in the Amazon biome. The database used for analyzes contained records of
1,402,287 animals born between the years 1950-2012. The population structure and
genetic diversity were investigated by estimated parameters with the information and
pedigree records made available by the Brazilian Association of Zebu creators.
Inferences about the effects of inbreeding were carried out by comparing models using
Bayesian methodology, the Deviance Information Criterion (DIC) was the test statistic
used. The completeness of the pedigree was 73.75%; 32.89%; and 11.69% in the first,
second and third generation respectively. The effective number of founders and
ancestors, the reference population, was 639 and 617, respectively. Assuming an
effect "bottleneck", virtually nil, estimated at 1.04. A contingent of 829 animals,
founders or not, explained 50% of the genetic variability of the population. The mean
generation interval, 7.46 years, can be considered high. The average coefficient of
inbreeding among the 18,647 inbred animals was 8.74%, being higher in the second
generation in the study. The effective population size ranged between 16.15 and
1810.8 animals over the evaluated periods. Estimates of weights at weaning, a year
and to yearling were 178.4 kg, 233 kg and 292.14 kg respectively. The comparison
between models with or without inbreeding allowed the conclusion that the inclusion of
this effect explains better the variation of the studied traits. Therefore, it is important to
monitor the mating to prevent that an increase in inbreeding can result in decreased
performance of the herds.
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