Danielle Maria Machado Ribeiro Azevêdo

Pedigree analysis on the population of Gir cattle in Northeast Brazil

The objective of this study was to characterize the population genetic structure of the Gir breed in the Northeast of Brazil. The data used in this study were taken from pedigree information of 8,897 Gir animals between 1957 and 2007, obtained from the Brazilian Zebu Breeders Association (ABCZ). The program ENDOG was used to estimate the parameters based on the probability gene origin. From the amount of the studied animals, 67.22%, 18.41% and 3.15% had complete pedigree only on the first, second and third parentage, respectively. The number of ancestors that contributed for the reference population was 2,755, of which only 171 explain the 50% genetic variability of the population. The actual number of founder herds was 168 and the effective number of founder herds was 22.3. The number of sire supplier herds was 22.16, 8.66 and 5.36 for fathers, grandfathers and great-grandfathers, respectively. The average coefficient of relatedness was estimated at 0.22%; the highest individual coefficient was 1.49%. The little variability of the current population is a result of the small number of effective founders and ancestors indicating the population evolved from a narrow genetic base.