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Home / Equine Research Bank / Acta Vet Scand / Physiological response to weight carrying and associations w...
Acta veterinaria Scandinavica2025; 67(1); 35; doi: 10.1186/s13028-025-00818-5

Physiological response to weight carrying and associations with conformation traits in Icelandic horses used for tour riding.

Abstract: Weight carrying capacity is an important trait in riding horses and it may be associated with conformation. This study examined the physiological response to a ridden incremental weight carrying test in 16 adult Icelandic horses used for tour riding. Horses carried 20% (BWR20%), 25% (BWR25%), 30% (BWR30%) and 35% (BWR35%) of their body weight (BW) in tölt (~ 5.7 m/seconds, 640 m/step), and associations with body measurements and back conformation (score) were examined. Horses were divided into two groups (narrow or broad back) and body measurements were collected. Plasma lactate was analysed in blood samples collected after each step in the exercise test, an exponential equation was fitted, and BW-ratio was calculated for 2, 3 and 4 mmol/L (BWRLa2, BWRLa3 and BWRLa4). Plasma creatine kinase (CK) and aspartate amino transferase (AST) were analysed at rest and 24 h post exercise. Results: Four out of 15 horses did not reach a plasma lactate concentration of 4 mmol/L, even at BWR35%. A positive correlation was found between chest width and BWRLa4 and between the difference between height at withers and croup and BWRLa2 (P < 0.05). Hock circumference and the difference between height at croup and back were negatively correlated with BWRLa2 (P < 0.05). The change in CK from rest to 24 h post exercise was negatively correlated with the difference between height at withers and height at back and croup (P < 0.05). Conclusions: The physiological response to weight carrying was relatively low. A wider chest, "uphill" conformation, straight backline and smaller hock circumference were associated with weight carrying capacity, but group (narrow or broad back) was not.
© 2025. The Author(s).
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Publication Date: 2025-06-19 PubMed ID: 40537779PubMed Central: PMC12180175DOI: 10.1186/s13028-025-00818-5Google Scholar: Lookup
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  • Journal Article

Summary

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This research investigated the physiological response of Icelandic horses to carrying various weights, and how it is related to their physical attributes. The study found that a wider chest, “uphill” body structure, straight backline, and smaller hock circumference could potentially enhance a horse’s capacity to carry weight.

Research Methodology

  • The study involved 16 adult Icelandic horses typically used for tour riding. The horses were asked to carry 20%, 25%, 30%, and 35% of their body weight in tölt (a special gait performed by Icelandic horses). The researchers sought to evaluate if and how body measurements and back conformation were connected with the horses’ physiological response to this exercise.
  • These horses were divided into two groups based on their back conformation- narrow or broad back. Specific body measurements were recorded for each horse.
  • Blood samples were collected from the horses after each exercise step and were used to analyze plasma lactate, creatine kinase (CK), and aspartate amino transferase (AST). CK and AST were analyzed at two different points- at rest and 24h after the exercise.

Findings

  • Results showed that four of the fifteen horses did not reach a plasma lactate concentration of 4 mmol/L, regardless of the weight ratio.
  • A positive relationship was observed between the horses’ chest width and weight ratio, as well as the difference between the height at the horse’s withers (shoulders) and croup (hindquarters), and the weight ratio.
  • In contrast, hock circumference (around the joint in the hind leg) and the difference between the height at croup and back were inversely related to weight ratio.
  • The change in CK levels from rest to post-exercise was inversely related to the difference in height at withers and back and croup.

Conclusion

  • The physiological response of the horses to carrying weight was relatively low. Certain physical attributes such as a wider chest, “uphill” body shape (where the horse’s back sloped upwards from hind to front), straight backline, and smaller hock circumference were associated with a more efficient weight carrying capacity.
  • The group division based on back conformation (narrow or broad) did not show a significant influence on the horse’s weight-carrying capacity.

Cite This Article

APA
Söderroos D, Stefánsdóttir GJ, Ragnarsson S, Gunnarsson V, Jansson A. (2025). Physiological response to weight carrying and associations with conformation traits in Icelandic horses used for tour riding. Acta Vet Scand, 67(1), 35. https://doi.org/10.1186/s13028-025-00818-5

Publication

Acta veterinaria Scandinavica
ISSN: 1751-0147
NlmUniqueID: 0370400
Country: England
Language: English
Volume: 67
Issue: 1
Pages: 35

Researcher Affiliations

Söderroos, Denise
  • Department of Animal Biosciences, Faculty of Veterinary Medicine and Animal Science, Swedish University of Agricultural Sciences, 750 07, Uppsala, Sweden. denise.soderroos@slu.se.
Stefánsdóttir, Guðrún Jóhanna
  • Department of Equine Science, Hólar University, 551, Sauðárkrókur, Iceland.
Ragnarsson, Sveinn
  • Department of Equine Science, Hólar University, 551, Sauðárkrókur, Iceland.
Gunnarsson, Víkingur
  • Department of Equine Science, Hólar University, 551, Sauðárkrókur, Iceland.
Jansson, Anna
  • Department of Animal Biosciences, Faculty of Veterinary Medicine and Animal Science, Swedish University of Agricultural Sciences, 750 07, Uppsala, Sweden.
  • Department of Equine Science, Hólar University, 551, Sauðárkrókur, Iceland.

MeSH Terms

  • Animals
  • Horses / physiology
  • Horses / anatomy & histology
  • Male
  • Physical Conditioning, Animal / physiology
  • Weight-Bearing / physiology
  • Female
  • Lactic Acid / blood
  • Body Weight
  • Creatine Kinase / blood
  • Iceland

Grant Funding

  • 19-005 / Icelandic Horse breed and the Agricultural Productivity Fund of Iceland

Conflict of Interest Statement

Declarations. Ethics approval and consent to participate: The study was carried out under Reg. 460/2017 on the protection of animals used for scientific purposes, as permitted by the Icelandic Food and Veterinary Authority, Ref. No. 2109502. Consent for publication: Written consent for publication of photos of the horses was obtained from the horse owners. Prior publication: Data included in this article have previously been published in the Proceedings of the 7th Animal Welfare Science Symposium, 3–4 June 2024, Uppsala, Sweden. Competing interests: The authors declare that they have no competing interests.

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