Brazilian Sport Horse: pedigree analysis of the Brasileiro de Hipismo breed

Brasileiro de Hipismo (BH) represents an open population that permits genetic input from breeds recognised by the World Breeding Federation for Sport Horses. The aim of this study was the genetic characterisation of the population as the first of a series aiming at the consolidating the current selection programme. The Brazilian Association of the Brazilian Sport Horse Breeders provided genealogical data from 1977 to 2011. A data bank containing 34,393 horses was analysed for population genetic parameters including: individual inbreeding (F), effective population size (N-e), effective number of founders (f(e)), effective number of ancestors (f(a)), and number of founder genome equivalents (f(g)). Analysis were run twice: for animals born until 1995 (PREVIOUS) and for those born in the last 15 years (15YEARS). N-e estimated via paired increase in coancestry consisted of 188.59 (+/- 3.24) animals. f(e) was 466 and 222 for PREVIOUS and 15YEARS, respectively. Ancestors were represented by f(a) of 274 and 129. Mean F for 15YEARS was 0.6%; 1444 animals were inbred, with mean inbreeding of 3.33%. The difference found in f(a) and f(e) parameters, between PREVIOUS and 15YEARS, indicated the loss of original alleles. The increase in contribution from some founders represents the breeder's preference for a few horses, without the negative effect of high inbreeding levels. Brasileiro de Hipismo genetic variability agrees with its large based formation history, and should allow for genetic gain of heritable traits through selection.