INBREEDING AND REPRODUCTIVE-PERFORMANCE IN STANDARDBRED HORSES

The relationship between inbreeding and both conception and foaling rates in Standardbred horses (trotters and pacers) was examined for 1194 breeding years. There was a statistically significant (P < 0.05) trend for conception and foaling rates to decrease with increased inbreeding; however, this relationship accounted for less than 2% of the variation. Additionally, the relationship between reproductive performance and inbreeding was not consistent between trotters and pacers. For trotters (F [inbreeding coefficient] = 0.103) there was a trend for an increase in conception and foaling rates with increased inbreeding, while for pacers (F = 0.074), reproductive performance decreased with increased inbreeding. Overall, inbreeding does not appear to be a significant factor influencing reproductive performance of Standardbred horses.