Preliminary heritability of complete rotation large colon volvulus in Thoroughbred broodmares.

Large colon volvulus (LCV) is a life-threatening form of colic that occurs when the large colon rotates 360° or more on its axis, resulting in colonic distention and ischaemia. Any horse can suffer from LCV, but the risk is greatest for periparturient Thoroughbred broodmares; the objective of this study was to estimate the heritability of LCV in these horses. The criteria for classification as an LCV case were being a Thoroughbred broodmare from one of three farms in central Kentucky and having had surgical correction for LCV. Controls were identified as Thoroughbred broodmares present on the same farms with no history of surgical colic. Thirty-nine cases and 191 controls were identified. Age of the LCV cases at the time of incident was significantly younger than that of the controls at the time of the study (P<0.0001). A total of 2223 horses were present when the five-generation pedigrees of the 230 study horses were combined. Heritability of LCV was estimated at 0.311±0.383 from the fit of a logit sire model with binomial data including year of birth and farm as fixed effects. Further data on broodmares from these and other farms will help to improve this estimate, which suggests the LCV is moderately heritable.