title: Heritability estimates of tarsocrural osteochondrosis and palmar/plantar first phalanx osteochondral fragments in Standardbred trotters.
abstract: BACKGROUND
  The pathogenesis of osteochondrosis (OC) and palmar/plantar first phalanx osteochondral fragments (POFs) is multifactorial, but specific knowledge of heritability is limited.
  
  
  OBJECTIVE
  To improve the precision of heritability estimates and to estimate the genetic correlation between tarsocrural OC and POFs in Standardbred trotters. Further aims were to examine whether the prevalence of OC/POFs was different in the American and French lineages that have contributed to the Norwegian population, and if the prevalence was affected by heterozygosity.
  
  
  METHODS
  Retrospective cohort study.
  
  
  METHODS
  Categorical data on tarsocrural OC and POFs from 2 radiographic studies performed in 1989 and 2007/2008 (n = 1217) were analysed with sire threshold models that included 230 sires.
  
  
  RESULTS
  Heritability of OC at the distal intermediate ridge of the tibia and/or the lateral trochlear ridge of the talus was estimated at 0.29 ± 0.15. For OC at the distal intermediate ridge of the tibia only, the estimate was 0.40 ± 0.17. Heritability of POFs in all 4 limbs was estimated at 0.23 ± 0.13; for metatarsophalangeal POFs this was 0.26 ± 0.13 and for medial metatarsophalangeal POFs 0.32 ± 0.14. Estimates of genetic correlation between OC and POFs ranged from 0.68 ± 0.27 to 0.73 ± 0.28 but were not significantly different from a zero-genetic correlation. Effects of lineages or heterozygosity were not observed.
  
  
  CONCLUSIONS
  This study confirmed a moderate to high heritability of tarsocrural OC and POF, providing further evidence of the heritable nature of these diseases. Examination of specific lesions yielded the highest heritability; therefore, breeding programmes and future genome-analysis studies should focus on predilection sites rather than the entire disease complex.
authors: Department of Companion Animal Clinical Sciences, Section for Equine Medicine and Surgery, The Norwegian School of Veterinary Science, Oslo, Norway; Department of Basic Sciences and Aquatic Medicine, The Norwegian School of Veterinary Science, Oslo, Norway.
authors: S
authors: S
authors: Lykkjen
authors: H F
authors: HF
authors: Olsen
authors: N I
authors: NI
authors: Dolvik
authors: A M
authors: AM
authors: Grøndahl
authors: K H
authors: KH
authors: Røed
authors: G
authors: G
authors: Klemetsdal
mesh_terms: D000818:Animals; D015331:Cohort Studies; D020022:Genetic Predisposition to Disease; D006734:Horse Diseases / Q000235:genetics*; D006736:Horses; D055034:Osteochondrosis / Q000235:genetics / Q000473:pathology / Q000662:veterinary*; D010375:Pedigree; D012189:Retrospective Studies; D013643:Tarsus, Animal / Q000473:pathology*
keywords: Standardbred; heritability; horse; osteochondral fragment; osteochondrosis