508 - Late-Breaking: Heritability and Validation of Sow Uterine Prolapse in the United States

Uterine prolapse impacts animal welfare and reduces sow farm profitability. In general, the incidence of uterine prolapse is higher in the United States than in other countries. Some suspected causes of uterine prolapse include water quality, vitamin deficiency, mycotoxins, and genetics. The objectives of this study were to: 1.) estimate the heritability of uterine prolapse; and 2.) to validate estimated breeding values (EBVs) for uterine prolapse in an independent, related population. Prolapse records collected from purebred females at a commercial multiplier (n = 16,434) and nucleus farm (n = 4,096) were used for training and validation, respectively. Phenotypes were recorded as the presence/absence of uterine prolapse at the sow level. Heritability estimates were derived from the training dataset by fitting year-season of insemination and parity at removal of the sow as fixed effects and animal as a random effect. Using the same model, validation was performed by regressing corrected offspring performance on sire EBV in the validation dataset. A pedigree- and a genomics-based relationship matrix were used for parameter estimation and the validation analysis, respectively. Incidence of uterine prolapse was heritable at 0.15 ± 0.02 and 0.22 ± 0.02 when analyzed using a linear vs. threshold model, respectively. Regression of corrected offspring performance on sire EBV resulted in a slope parameter of 0.40 (95%-CI; 0.27 - 0.54, including the expected value of 0.5), indicating that sire EBV is predictive of uterine prolapse among his offspring. In conclusion, these results show that uterine prolapse is lowly-to-moderately heritable, and therefore, mainly due to environmental factors. Higher incidence of uterine prolapse within the United States vs. other geographic locations confirms the existence of a strong environmental component. Genetic selection can be used to address genetic factors, but identifying/mitigating environmental triggers remains critical to reducing the incidence of uterine prolapse within the U.S. swine industry.