Use of an analgesic to identify pain-related indicators of lameness in sows

• Injection of meloxicam decreased the stepping frequency after feeding in lame sows.
• Injection of meloxicam tended to increase standing time after feeding in lame sows.
• However, meloxicam effects on most lameness variables were limited in the 8 h following injection.
• More research is needed to identify pathology-specific indicators of pain-related lameness.

Lameness in sows may be associated with pain and poor welfare and requires early detection and treatment. The objective of this study was to use the non-steroidal anti-inflammatory drug meloxicam, as a short-term analgesic to identify characteristics of pain-related lameness in sows. A total of 44 pregnant sows were selected from two experimental sites, and used in a 2×2 factorial design. Sows were visually categorized as either non-lame or lame (none with severe lameness), and were either assigned to a placebo (saline) or meloxicam (0.4 mg/kg body weight) treatment. Lameness was assessed using a force plate, kinematic and accelerometer tools on the day before, and after a single intramuscular injection of treatment solution. Data were collected in the same order and at the same time on both days, starting at 7:45, 9:15 and 12:15 for accelerometers, force plate and kinematics, respectively. Before treatment, lame sows made a greater number of steps per min than sound sows (P=0.013), and had a tendency to have a lower contralateral ratio of weight applied between the hind legs than sound sows (P=0.062). No other differences were observed between lame and sound sows before treatment. Injection of meloxicam decreased the stepping frequency of the left hind legs (P=0.014), increased the ratio of tarsal joint angle amplitude between contralateral hind legs (P=0.05), and tended to increase standing time after feeding in lame sows (P=0.09), indicating an improvement of the lameness condition and at least a short-term analgesic effect of meloxicam. Overall, meloxicam effects on lameness variables were limited. The wide variability in the underlying clinical causes, severity and duration of these naturally occurring lameness cases, as well as the timing of lameness assessment in relation to treatment injection may explain the relative lack of treatment effects on kinematics and force plate variables. More research is needed to identify pathology-specific indicators of pain-related lameness.