Lameness is consistently better at predicting broiler chicken performance in mobility tests than other broiler characteristics

Abstract

To determine whether lame broilers are in pain it is necessary to compare measures of lameness and mobility before and after analgesic treatment. Such measures should not be unduly affected by other bird characteristics. This study assessed the performance of lame (gait score, GS 3-4) and non-lame (GS 0-1) broilers using two mobility tests: (i) a novel test to assess broiler ability to access resources when housed in groups (Group Obstacle test); and (ii) a Latency-to-Lie (LTL) test. Outcome test measures included number of obstacle crossings, latency to cross an obstacle, and time taken to sit in shallow water. Associations between outcome test measures and other bird characteristics (established lameness risk-factors), including strain, sex, age, mass, contact dermatitis and pathology, were also investigated. The performance of high-GS and low-GS broilers differed in both mobility tests and no other bird characteristics were as consistent a predictor as lameness. This demonstrates that mobility impairments are closely related to lameness assessed using GS, and that there is a component of lameness that cannot be explained by other bird characteristics (eg being male and heavy). This component may represent pain or discomfort. Both mobility tests are suitable for further application with analgesic testing to classify lameness-associated pain in broilers.

Effects of carprofen, meloxicam and butorphanol on broiler chickens’ performance in mobility tests

“…Both drugs were also successful in reversing hyperalgesia (indicated by a lower nociceptive threshold) associated with induced hock inflammation (Caplen et al, 2013b). Finally, meloxicam elevated nociceptive threshold in lame commercial broilers, though this group of birds did not show hyperalgesia before treatment (Hothersall et al, 2014).…”

“…to avoid a mildly aversive experience (Caplen et al, 2014). In a related study, lameness was also associated with altered thermal nociceptive threshold (Hothersall et al, 2014). Importantly, lameness was the most consistent predictor of performance across these tests: other factors explained less variability in results or became non-significant when lameness was included in the models.…”

“…Surprisingly, however, subcutaneous butorphanol at 4mg/kg did not have any significant effect on nociceptive threshold in broilers up to 2 hours after administration (Hothersall et al, 2014).…”

“…Lame broilers made fewer, later crossings than non-lame broilers in an obstacle test and had a shorter Latency to Lie (LTL) in a shallow water bath -i.e. to avoid a mildly aversive experience (Caplen et al, 2014). In a related study, lameness was also associated with altered thermal nociceptive threshold (Hothersall et al, 2014).…”

“…Based on these data and pilot studies, we carried out exploratory studies to examine the effect of two NSAIDs (5 mg/kg meloxicam and 35 mg/kg carprofen) and an opioid (4 mg/kg butorphanol tartrate) on performance in the Obstacle and LTL tests described in Caplen et al (2014). The aim was to determine whether differences in mobility between lame and non-lame birds could be reversed or reduced by analgesic treatment.…”