Equis ISSN 2398-2977

Musculoskeletal: conformation

Contributor(s): Steve Adair, Graham Munroe, Vetstream Ltd, Chris Whitton

Conformation and performance

Introduction
  • Conformation, when used for veterinary purposes, describes anatomical form in relation to biomechanical function.
  • Traditionally, conformation is a subjective analysis of body outline or shape, but attempts to assess a horse's soundness by subjective judgement of skeletal lengths and angles is unreliable.
  • Exact relationship between conformation, performance and soundness is yet to be described.
  • Poor conformation contributes to or causes some lamenesses - it may determine the useful working life of a horse; but it is rare to find a horse with 'perfect' conformation.

Objective measuring techniques

  • Paper markers: glued to palpable and identifiable anatomical landmarks for standard reference points.
  • Measuring tape: to measure circumference of carpus, cannon, chest and some distances.
  • Box level measuring standard: height at withers, back and croup.
  • Cross-bar: for lengths of body, head, limbs; depth of chest, width of breast and pelvis.
  • Calipers: for width of head, cannon bones.
  • Goniometer: joint angles, inclinations of shoulder and pelvis.
  • For comparison with other horses, measurements are expressed in percentage of height of withers; or limb details as percentage of limb length.

Relationship with performance

  • Little scientific information; most studies use objective measurements to compare good and bad performers.
  • Standardbred  Standardbred  : possible that up to 10% of variation in performance can be attributed to conformation; better performers have the following characteristics:
    • Light weight.
    • Tall withers.
    • Normal size hooves.
    • Not tied-in at knees or hocks.
    • Outwardly rotated limb axes.
    • Large shoulder and stifle angles.
  • Showjumpers:
    • Wider breast and pelvis.
    • Greater chest girth.
    • Longer pelvis.
    • Smaller angle between femur and horizontal plane.
    • Compared to dressage horses, showjumpers tend to be higher at the withers.
    • Height at withers and large hock angles may correlate with competitive performance in both types.
  • Warmblood  Dutch warmblood  :
    • Showjumpers and dressage horses: higher at the withers and more sloping scapulae and larger hock angles.
    • Showjumpers: smaller pelvic inclination, smaller hip and fetlock angles.
    • Dressage horses: shorter neck and tibia, larger elbow angle, larger angle between the femur and the horizontal plane.

Relationship with soundness

  • Little scientific information, but relationship between bone health and conformation is of interest to researchers and private practitioners.
  • Divergence from correct conformation   →   increase stress to bones and joints and leads to injury.
  • Standardbred  Standardbred  : better if straight limb and toe-axes; poorer soundness noted if:
    • Very big or small.
    • Relatively short limbs.
    • Abnormally sized hooves.
    • Tied in at knees or hocks.
    • Curby or sickle hocks   Hindlimb: sickle hocks 01    Hindlimb: sickle hocks 02  .
    • Angled fetlocks.
  • In addition, those with hock osteochondrosis   Bone: osteochondrosis  are likely to be heavier, have higher weight gain, a larger circumference of the carpus and cannon; some relationship between outward rotation of hindlimb axes and osteochondrosis lesions in the hock, and plantar fragments in the fetlock.

Body conformation

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Forelimb conformation

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Hindlimb conformation

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Foot conformation

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Terminology

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Further Reading

Publications

Refereed papers
  • Recent references fromPubMed
  • Becker A C, Stock K F & Distl O (2013)Correlations of unfavorable movement characteristics in warmblood foals and mares with routinely assessed conformation and performance traits. Animal7(1), 11-21PubMed.
  • Unt V E, Evans J, Reed S R, Pfau T & Weller R (2010)Variation in frontal plane joint angles in horses. Equine Vet J Suppl38, 444-450PubMed
  • White J M, Mellor D J, Duz M, Lischer C J & Voute L C (2008)Diagnostic accuracy of digital photography and image analysis for the measurement of foot conformation in the horse. Equine Vet J40(7), 623-628PubMed.
  • Wilson A (2007)The role of biomechanics in the study of conformation and its relationship to orthopaedic health. Equine Vet J39(1), 14-16PubMed.
  • Gnagey L et al(2006)Effect of standing tarsal angle on joint kinematics and kinetics. Equine Vet J38(7), 628-633PubMed.
  • Love S et al(2006)Prevalence, heritability and significance of musculoskeletal conformational traits in Thoroughbred yearlings. Equine Vet J38(7), 597-603PubMed.
  • Santschi E M et al(2006)Carpal and fetlock conformation of the juvenile Thoroughbred from birth to yearling auction age. Equine Vet J38(7), 604-609PubMed.
  • van Weeren P R & Crevier-Denoix N (2006)Equine conformation: clues to performance and soundness? Equine Vet J38(7), 591-596PubMed.
  • Weller R et al(2006)Variation in conformation in a cohort of National Hunt racehorses. Equine Vet J38(7), 616-621PubMed.
  • Weller R et al(2006)The effect of conformation on orthopaedic health and performance in a cohort of National Hunt racehorses: preliminary results. Equine Vet J38(7), 622-627PubMed.
  • Carroll C L & Huntington P J (1988)Body condition scoring and weight estimation of horses. Equine Vet J20, 41-45PubMed.

Other sources of information

  • McIlwraith C W, Anderson T A, Douay P, Goodman N L & Overly L R (2003)Role of Conformation in Musculoskeletal Problems in the Racing Thoroughbred and Racing Quarter Horse.In: Proc 49th AAEP Convention.pp 59-61.
  • Stashak T (1987)The Relationship Between Conformation and Lameness.In: Adam's Lameness in Horses.Ed: Stashak T. Lea & Febiger, Philadelphia. ISBN 0-8121-0980-5.


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