Pain associated with poultry lameness is poorly understood. The anti-nociceptive properties of two non-steroidal anti-inflammatory drugs (
NSAIDs) were evaluated using threshold testing in combination with an acute inflammatory
arthropathy model. Broilers were tested in six groups (n=8 per group). Each group underwent a treatment (saline,
meloxicam (3 or 5mg/kg) or
carprofen (15 or 25mg/kg)) and a procedure (Induced (
arthropathy-induction) or
sham (
sham-handling)) prior to testing. Induced groups had Freund's complete adjuvant injected intra-articularly into the left intertarsal joint (hock). A ramped thermal stimulus (1°C/s) was applied to the skin of the left metatarsal. Data were analysed using random-intercept multi-level models. Saline-induced birds had a significantly higher skin temperature (± SD) than saline-
sham birds (37.6 ± 0.8°C vs. 36.5 ± 0.5°C; Z=-3.47, P<0.001), consistent with an inflammatory response. Saline was associated with significantly lower thermal thresholds (TT) than
analgesic treatment (
meloxicam: Z=2.72, P=0.007;
carprofen: Z=2.58, P=0.010) in induced birds. Saline-induced birds also had significantly lower TT than saline-
sham birds (Z=-2.17, P=0.030). This study found direct evidence of an association between inflammatory
arthropathies and
thermal hyperalgesia, and showed that
NSAID treatment maintained baseline thermal sensitivity (via anti-nociception). Quantification of nociceptive responsiveness in a predictable broiler
pain model identified thermal anti-hyperalgesic properties of two
NSAIDs, which suggested that therapeutically effective treatment was provided at the doses administered. Such validation of
analgesic strategies will increase the understanding of
pain associated with specific natural broiler lameness types.