Genetic parameters for speed index in quarter horse

The aim of this research was to study genetic parameters for speed index (SI) in Quarter Horse. The data supplied by the Jockey Club de Sorocaba secretary, consisted of 2521 races and 8968 speed index records covering a ten-year period (from 1994 to 2003). The variance component was obtained by derivate-free restricted maximum likelihood method. The model used contained fixed effects of race, sex, age and origin, and the random animal and permanent environmental effects. The repeatibility estimates ranged between 0.25 (365 m) and 0.39 (402 m) and the heritability ones between 0.01 (320 m) and 0.13 (365 m). This indicates that the selection based on animal phenotypic values induce small genetic changes in this index

Precocidade e desempenho em corridas de cavalos Puro-Sangue Inglês brasileiros

Genetic and phenotypic correlations among age at the first race (F) and racetrack performance traits (number of victories (NV), number of placements in top 5 (N5), percentage of victories (PV), percentage of placementes in top 5 (P5), and number of starts (NS)) were estimated for 1.138 Brazilian Thoroughbred using MTDFREML software. The results indicates that horses with a high genetic merit for NV and PV were those with a low genetic potential for F. Phenotypically, animals with greater NS and N5 were those with lower F