title: Factors affecting mechanical nociceptive thresholds in healthy sows.
abstract: OBJECTIVE
  To describe anatomical and methodological factors influencing mechanical nociceptive thresholds (MNTs) and intra-site variability in healthy sows.
  
  
  METHODS
  Prospective, randomized validation.
  
  
  METHODS
  Eight pregnant, healthy, mixed-parity sows (176-269 kg).
  
  
  METHODS
  Repeated MNT measurements were taken: 1) with a hand-held probe and a limb-mounted actuator connected to a digital algometer; 2) at nine landmarks on the limbs and tail; and 3) at 1 and 3 minute intervals. Data were analysed using linear mixed regression models.
  
  
  RESULTS
  The MNTs (±SEM) of the limbs were lower with the probe (14.7 ± 1.2 N) than with the actuator (21.3 ± 1.2 N; p < 0.001), in the pelvic versus the thoracic limbs (16.7 ± 1.2 versus 19.2 ± 1.2 N; p < 0.001), and in the lateral versus the dorsal metatarsi and metacarpi (17.6 ± 1.2 versus 18.4 ± 1.2 N; p = 0.002). MNTs were higher in all subsequent measurements compared with the first (p < 0.001) and in the morning compared with the afternoon (p = 0.04). We found no evidence of MNT differences based on interval between consecutive measurements (1 versus 3 minutes). Variability was lower in the thoracic limbs [mean back-transformed log10 coefficient of variation (CV) ± SE = 25.5 ± 1.5% versus 30.6 ± 1.5% in the pelvic limbs; p < 0.001], with the actuator (22.7 ± 1.5% versus 33.4 ± 1.5% with the probe; p < 0.001), and on the left (CV = 26.9 ± 1.5% versus 29.3 ± 1.5% on the right; p = 0.01). Tail data (probe only) were analysed separately: mean MNT (± SE) was 11.7 (±1.8); MNT increased in days 3-6 of testing compared with day 1 (p < 0.001). The mean CV (±SE) was 38.9% (±1.1%).
  
  
  CONCLUSIONS
  MNTs and intra-site variability in healthy sows were affected by several factors, indicating that this methodology requires considerable attention to detail.
authors.affiliation: Animal Sciences Unit, Institute for Agricultural and Fisheries Research, Melle, Belgium.|Department of Reproduction, Obstetrics and Herd Health, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium.
authors.forename: Elena
authors.initials: E
authors.lastname: Nalon
authors.affiliation: Department of Reproduction, Obstetrics and Herd Health, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium.
authors.forename: Dominiek
authors.initials: D
authors.lastname: Maes
authors.affiliation: Department of Reproduction, Obstetrics and Herd Health, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium.
authors.forename: Sofie
authors.initials: S
authors.lastname: Piepers
authors.affiliation: Taylor Monroe, Little Downham, Ely, Cambridgeshire, UK.
authors.forename: Polly
authors.initials: P
authors.lastname: Taylor
authors.affiliation: Animal Sciences Unit, Institute for Agricultural and Fisheries Research, Melle, Belgium.|Department of Nutrition, Genetics and Ethology, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium.
authors.forename: Miriam M J
authors.initials: MM
authors.lastname: van Riet
authors.affiliation: Department of Nutrition, Genetics and Ethology, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium.
authors.forename: Geert P J
authors.initials: GP
authors.lastname: Janssens
authors.affiliation: Animal Sciences Unit, Institute for Agricultural and Fisheries Research, Melle, Belgium.
authors.forename: Sam
authors.initials: S
authors.lastname: Millet
authors.affiliation: Animal Sciences Unit, Institute for Agricultural and Fisheries Research, Melle, Belgium.|Department of Nutrition, Genetics and Ethology, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium.
authors.forename: Frank A M
authors.initials: FA
authors.lastname: Tuyttens
mesh_terms: D000818:Animals; D005260:Female; D017288:Pain Threshold; D010812:Physical Stimulation; D011247:Pregnancy; D011446:Prospective Studies; D013552:Swine
keywords: measurement; mechanical nociceptive threshold; pain; pig; variability