title: Heritability of racing durability traits in the Australian and Hong Kong Thoroughbred racing populations.
abstract: BACKGROUND
  Many attempts have been made to improve the well-being of racing Thoroughbreds through improvements in management and veterinary care. However, these attempts are often limited by the industry's ability to regulate a large number of environmental variables and as a result have arguably had limited success in providing long-lasting change for the breed.
  
  
  OBJECTIVE
  To identify heritable durability traits for Thoroughbred horses racing in Australia and Hong Kong.
  
  
  METHODS
  Heritability analysis of a longitudinal dataset.
  
  
  METHODS
  Performance data on the Thoroughbred populations racing in Australia and Hong Kong between 2000 and 2011 (n = 168,993) were used to estimate the heritabilities and probability values of fixed effects and covariates for a range of racing durability traits. Heritabilities for all durability traits were estimated using a single trait animal model. Each model included, as a minimum, the effects of sex and trainer.
  
  
  RESULTS
  Racing longevity (0.12 ± 0.01), racing persistence (0.10 ± 0.01), racing frequency (0.03 ± 0.01), spells (a time period between consecutive races, official trials and/or jump-outs greater than 90 days in length) per year (0.05 ± 0.01), spells per 10 starts (0.03 ± 0.01) and variation of days between races (0.08 ± 0.03) were all significantly heritable for horses racing in Australia. Racing longevity (0.08 ± 0.02), racing persistence (0.04 ± 0.02), spells per year (0.06 ± 0.02) and spells per 10 starts (0.11 ± 0.04) were significantly heritable for horses racing in Hong Kong.
  
  
  CONCLUSIONS
  The heritabilities estimated for durability traits in this study provide support for the successful and practical application of genetic selection methodologies to improving the well-being of racing Thoroughbreds.
authors.affiliation: Faculty of Veterinary Science, University of Sydney, Sydney, New South Wales, Australia.
authors.forename: B D
authors.initials: BD
authors.lastname: Velie
authors.affiliation: Faculty of Veterinary Science, University of Sydney, Sydney, New South Wales, Australia.
authors.forename: N A
authors.initials: NA
authors.lastname: Hamilton
authors.affiliation: Faculty of Veterinary Science, University of Sydney, Sydney, New South Wales, Australia.
authors.forename: C M
authors.initials: CM
authors.lastname: Wade
mesh_terms: D000822:Animal Husbandry; D000827:Animal Welfare; D000818:Animals; D001947:Breeding; D020022:Genetic Predisposition to Disease; D006734:Horse Diseases / Q000235:genetics*; D006736:Horses; D012420:Running; D012641:Selection, Genetic; D013177:Sports; D014947:Wounds and Injuries / Q000235:genetics / Q000662:veterinary*
keywords: disease; fitness; horse; racehorse; well-being