Data on 71,991 animals of the Campolina horse breed studbook recorded from 1951 to 2000 were used to describe the population structure of the breed. Most of the animals (86.6%) originated from the Southeast States of Brazil. The average number of births per year was 1,159, and the maximum number of births (5,107) was observed in 1991. From the total of 3,361 Campolina breeders and 4,848 Campolina owners, respectively, 50.3% and 60.3% owned no more than five animals. Concerning progeny number, 53.3% of the 17,680 mares had less than two sibs and 51.7% of 2,418 stallions had less than 10 sibs. The average and maximum number of births for the mares were, respectively, 3.1 and 20. For the stallions, these numbers were 22.2 and 531, respectively. Considering all data structure, the effective population size was 8,509 animals, and the average inbreeding coefficient for the population was close to zero. The highest generation number was 6.5 and the average generation interval was 8.7 years. The inbred animals had an average inbreeding coefficient of 6.1%, with and increase rate of 1.9% per generation.
horse; inbreeding; generation interval
