Strategies to reduce the pain of tail docking in piglets

Tail docking is a common practice to prevent tail biting in piglets and strategies to provide pain relief for the short-term pain (Morrison et al. 2013) associated with this procedure are being investigated. The aim of this experiment was to assess the efficacy of the cauterisation technique with or without pain relief (meloxicam) in mitigating the acute stress response to tail docking. The hypothesis was that cauterisation and meloxicam would mitigate the stress response and reduce pain-related behaviours compared to the cauterisation or clipping the tail without meloxicam.

Seventy-two sows (Large White × Landrace; PrimeGro™ Genetics, Corowa, NSW) and their litters were used. Fostering was conducted in the first 24 h post-birth. Six entire male piglets were selected per litter at 2 days post-farrowing (432 piglets). Piglets were randomly allocated to the following treatments: (1) No Handling; (2) Sham: Handling; (3) Clipper: Tail docked using sanitised clippers; (4) Cauteriser: Tail docked using a cauterising iron (Stericut Tail Docker, Cotran Corp., Portsmouth, RI, USA); (5) Meloxicam + Clipper; and (6) Meloxicam + Cauteriser. Meloxicam treatments used Metacam (Boehringer Ingelheim, Sydney, NSW, Australia)^® at 5 mg/mL injected intra muscularly 1 h before tail docking. Piglets in all treatments were handled in the same manner, for the same duration, by the same two technicians. The tail was cut ~2 cm from the base. Blood samples were collected via jugular venipuncture at 15 and 30 min and analysed for total plasma cortisol using an extracted radioimmunoassay (Immuchem™ Coated Tube Cortisol RIA kits; MP Biomedicals, Belgium). Pain-related behaviour was assessed by measuring the frequency of escape attempts (Marchant-Forde et al. 2009) and duration of vocalisations during treatment. After treatment, behaviour was recorded using mounted cameras (Signet Model QV-3063). The behaviour (postures, states and pain-related behaviours; Hay et al. 2003) were measured by continuously observing each piglet for 1 min every 5 min for 1 h post-treatment. Statistical analyses were performed using SPSS (v21.0, IBM, Armonk, NY, USA). Univariate GLM was used, with each pig as the experimental unit and sow as a random factor and post-hoc tests were conducted using least significant difference tests.

In comparison to the Sham treatment, cortisol concentrations at 15 min were higher (P < 0.05) in the Clipper and Cauterisation treatment whereas the Meloxicam + Clipper and Meloxicam + Cauteriser treatments were similar to the Sham. At 30 min post-docking, in comparison to the Sham treatment, cortisol concentrations were higher (P < 0.05) in the Clipper treatment (Table 1). The Cauterisation, Meloxicam+Clipper and Meloxicam + Cauteriser treatments were similar to the Sham treatment. The duration of vocalisations and frequency of escape attempts during treatment were greater (P < 0.05) in all of the tail docking treatments compared to the Sham treatment. Piglets in the Clipper treatment spent more (P < 0.05) time with their head lowered compared to all other treatments and there were no significant differences (P > 0.05) between treatments in other postures and states observed. Cauterisation appears to be less aversive than the Clipper technique, based on the physiological stress response. The administration of Meloxicam did not mitigate the behavioural response during tail docking, however, it mitigated the physiological stress response. The commercial administration of meloxicam requires consideration before it is recommended for use compared to cauterisation alone.

Table 1.  Mean total plasma cortisol (ng/mL) concentrations at 15 and 30 min post-treatment