title: The effect of weightbearing and limb load cycling on equine lamellar perfusion and energy metabolism measured using tissue microdialysis.
abstract: BACKGROUND
  Lamellar perfusion is thought to be affected by weightbearing and limb load cycling; this may be critical in the development of supporting limb laminitis.
  
  
  OBJECTIVE
  To document the effects of unilateral weightbearing and altered limb load cycling on lamellar energy metabolism and perfusion.
  
  
  METHODS
  Randomised, controlled (within subject), experimental trial.
  
  
  METHODS
  Nine Standardbred horses were instrumented with microdialysis probes in the foot lamellar tissue and skin (over the tail base). Urea (20 mmol/l) was added to the perfusate. Samples were collected every 15 min for a 1 h control period, then during periods of unilateral weightbearing (opposite limb held off the ground for 1 h); enhanced static limb load cycling (instrumented limb lifted every 10 s for 30 min); reduced limb load cycling activity (i.v. detomidine sedation) and continuous walking (30 min). Dialysate concentrations of glucose, lactate, pyruvate and urea were measured and lactate:glucose (L:G) and lactate:pyruvate (L:P) ratios were calculated. For each intervention, values were compared with baseline using nonparametric statistical testing.
  
  
  RESULTS
  Lamellar dialysate glucose increased and L:G decreased significantly during enhanced static limb load cycling. Glucose and pyruvate increased, and L:G, L:P and urea decreased significantly during walking. Simultaneous skin dialysate values did not change significantly. There were no significant dialysate changes during unilateral weightbearing or after detomidine administration, but only the latter resulted in a significant decrease in limb load cycling frequency.
  
  
  CONCLUSIONS
  Increases in limb load cycling frequency (particularly walking) caused dialysate changes consistent with increased lamellar perfusion. Unilateral weightbearing (1 h) and a sedation-induced reduction in limb load cycling frequency did not have a detectable effect on lamellar perfusion. More research is needed to confirm the role of hypoperfusion in supporting limb laminitis, but strategies to increase limb load cycling may be important for prevention.
authors.affiliation: Australian Equine Laminitis Research Unit, School of Veterinary Science, The University of Queensland, Gatton, Australia.
authors.forename: C E
authors.initials: CE
authors.lastname: Medina-Torres
authors.affiliation: Australian Equine Laminitis Research Unit, School of Veterinary Science, The University of Queensland, Gatton, Australia.
authors.forename: C
authors.initials: C
authors.lastname: Underwood
authors.affiliation: Australian Equine Laminitis Research Unit, School of Veterinary Science, The University of Queensland, Gatton, Australia.
authors.forename: C C
authors.initials: CC
authors.lastname: Pollitt
authors.affiliation: Australian Equine Laminitis Research Unit, School of Veterinary Science, The University of Queensland, Gatton, Australia.
authors.forename: E M
authors.initials: EM
authors.lastname: Castro-Olivera
authors.affiliation: Metabolomics Australia, Queensland Node, Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, St Lucia, Australia.
authors.forename: M P
authors.initials: MP
authors.lastname: Hodson
authors.affiliation: Department of Clinical Studies, New Bolton Center, School of Veterinary Medicine, University of Pennsylvania, Kennett Square, USA.
authors.forename: D W
authors.initials: DW
authors.lastname: Richardson
authors.affiliation: Australian Equine Laminitis Research Unit, School of Veterinary Science, The University of Queensland, Gatton, Australia.
authors.forename: A W
authors.initials: AW
authors.lastname: van Eps
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D005528:Foot / Q000502:physiology*; D006736:Horses / Q000502:physiology*; D017551:Microdialysis / Q000295:instrumentation / Q000379:methods / Q000662:veterinary*; D008991:Monitoring, Physiologic / Q000295:instrumentation / Q000379:methods / Q000662:veterinary*; D016138:Walking
keywords: blood flow; horse; supporting limb laminitis; weightbearing