Pekin ducks are motivated to access their nest site and exhibit a stress-induced hyperthermia when unable to do so.

The origins of floor-laying in ducks could be low motivation for a nest, or stress related to difficulties with accessing a nest (e.g. competition). Using a behavioural demand test, we investigated if increasing the work required to access their nest impacted ducks' behaviour and two indicators of stress: egg corticosterone concentration and elevation of core body temperature (stress-induced hyperthermia (SIH)). Twelve laying Pekin ducks previously trained in an operant push-door task were required to use a push-door to access their nest. The door was loaded with increasing weight (0-160% of individual BW, four nights per workload) and eventually blocked to prevent nest access. Before testing, temperature data loggers were implanted in the abdomen. Eggs were collected daily to measure corticosterone concentrations. Behaviour towards the push-door was quantified. Three birds were excluded from the experiment at an early stage. Five of the nine remaining birds pushed all workloads up to 160% BW and attempted to pass the blocked door, with another two birds pushing up to 80 and 140% BW. For those that pushed at all workloads (n = 5) the area under the curve (AUC) of hyperthermia was larger at workloads of 80% (P < 0.001), 120% (P < 0.01), 140% (P < 0.001), 160% (P < 0.001), and when the door was blocked (P < 0.001), compared with 0%. On the first night when the door was blocked, all five birds pushed more at the door, but no attempts were made to push on the following 3 nights, yet the AUC of hyperthermia did not differ between nights 2-4 of the blocked door, compared with the first night that the door was blocked. Increasing workload and inability to access the nest had no effect on corticosterone in egg albumen. It was concluded that laying Pekin ducks were motivated to access a nest. Although it was not possible to differentiate metabolic from psychogenic stress on the first night that nest access was denied, we suggest that the occurrence of hyperthermia on the subsequent nights was due to SIH resulting from frustration at their inability to use their preferred nest. Floor-laying therefore is unlikely due solely to low nest-seeking motivation. Egg corticosterone was not a relevant indicator of acute stress. Strategies to improve nest availability (e.g. decreasing competition) could improve the welfare of commercial ducks.

Pain-related behavior was not observed in dairy cattle in the days after liver biopsy, regardless of whether NSAIDs were administered.

For liver biopsy in cattle, it is routine practice to only provide local anesthesia (LA) to the skin and muscle layers, with visceral tissues remaining unanesthetized. Cattle being biopsied may therefore benefit from additional analgesia. This study aimed to determine if non-steroidal anti-inflammatory drugs would decrease post-biopsy pain in cattle. Twenty-four dairy cows were allocated into four treatment groups: biopsy under LA only; biopsy under LA with ketoprofen; biopsy under LA with meloxicam; and a sham-biopsied control group. Behavior was observed for 4h immediately following biopsy, and for 2h each day for the first three days after biopsy. No significant differences in behavior were found between any treatment groups on any day. This suggests that any post-biopsy pain present was not of enough significance to alter the cows' normal behavior patterns. Without identifying post-biopsy pain, it is not possible to determine what effect NSAID analgesia may have had on alleviating it.

Assessment of a carbon dioxide laser for the measurement of thermal nociceptive thresholds following intramuscular administration of analgesic drugs in pain-free female cats.

OBJECTIVE: To assess the potential of a thermal carbon dioxide (CO2) laser to explore antinociception in pain-free cats. STUDY DESIGN: Experimental, prospective, blinded, randomized study. ANIMALS: Sixty healthy adult female cats with a (mean±standard deviation) weight of 3.3±0.6 kg. METHODS: Cats were systematically allocated to one of six treatments: saline 0.2 mL per cat; morphine 0.5 mg kg(-1); buprenorphine 20 µg kg(-1); medetomidine 2 µg kg(-1); tramadol 2 mg kg(-1), and ketoprofen 2 mg kg(-1). Latency to respond to thermal stimulation was assessed at baseline and at intervals of 15-30, 30-45, 45-60, 60-75, 90-105 and 120-135 minutes. Thermal thresholds were assessed using time to respond behaviourally to stimulation with a 500 mW CO2 laser. Within-treatment differences in response latency were assessed using Friedman's test. Differences amongst treatments were assessed using independent Kruskal-Wallis tests. Where significant effects were identified, pairwise comparisons were conducted to elucidate the direction of the effect. RESULTS: Cats treated with morphine (χ2=12.90, df=6, p=0.045) and tramadol (χ2=20.28, df=6, p=0.002) showed significant increases in latency to respond. However, subsequent pairwise comparisons indicated that differences in latencies at specific time-points were significant (p<0.05) only for tramadol at 60-75 and 90-105 minutes after administration (21.9 and 43.6 seconds, respectively) in comparison with baseline (11.0 seconds). No significant pairwise comparisons were found within the morphine treatment. Injections of saline, ketoprofen, medetomidine or buprenorphine showed no significant effect on latency to respond. CONCLUSIONS AND CLINICAL RELEVANCE: The CO2 laser technique may have utility in the assessment of thermal nociceptive thresholds in pain-free cats after analgesic administration and may provide a simpler alternative to existing systems. Further exploration is required to examine its sensitivity and comparative utility.