Physiological response to weight carrying and associations with conformation

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

Acta Vet Scand. 2025 Jun 19;67(1):35. doi: 10.1186/s13028-025-00818-5.
Authors
Denise Söderroos 1 , Guðrún Jóhanna Stefánsdóttir 2 , Sveinn Ragnarsson 2 , Víkingur Gunnarsson 2 , Anna Jansson 3 2
Affiliations

1 Department of Animal Biosciences, Faculty of Veterinary Medicine and Animal Science, Swedish University of Agricultural Sciences, 750 07, Uppsala, Sweden. denise.soderroos@slu.se.
2 Department of Equine Science, Hólar University, 551, Sauðárkrókur, Iceland.
3 Department of Animal Biosciences, Faculty of Veterinary Medicine and Animal Science, Swedish University of Agricultural Sciences, 750 07, Uppsala, Sweden.

PMID: 40537779
DOI: 10.1186/s13028-025-00818-5

Abstract

Background: 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.Keywords: Back; Body measurements; Equine; Rider weight; Weight carrying exercise test.© 2025. The Author(s).