The routine castration and tail docking of lambs with rubber rings has been shown, using behavioural and physiological methods, to be painful. To improve the welfare of lambs during such routine procedures it is important to validate the methods for assessment of pain. This was considered ethically acceptable, as groups of lambs would be subjected to decreasingly severe castration and tail docking treatments.

Forty-two lambs, 5-6 days of age, were subjected to rubber ring castration and tail docking of different severities. Six treatments were ranked, before the experiment, in descending order of severity according to the amount and sensitivity of the tissues involved and the established effectiveness of local anaesthetic. Treatments were as follows: (1) bilateral castration and tail docking, (2) bilateral castration, (3) unilateral castration, (4) short scrotum castration, (5) short scrotum castration with local anaesthetic (LA), (6) handled untreated control lambs (H). A seventh group (n=7) of lambs were tail docked. Because this treatment did not involve visceral tissue, it was not ranked prior to treatment, although previous experience suggested that this procedure was less painful than bilateral castration. Nine active behaviours (getting up and down, rolling and jumping, foot stamping and kicking, easing quarters, tail wagging, head turning and vocalisation), thirteen lying and standing postures, and changes in plasma cortisol were monitored for 180 min after treatment. Eleven 2-ml blood samples (using Sarstedt Monovets and 20g x 1" needles) were collected by jugular venipuncture. Two pre-treatment samples were taken and at 12, 24, 36, 48, 60, 72, 96, 132 and 180 min after treatment. Behaviour data was collected live on to paper using one observer and one writer for the first 60 min and one observer/ writer thereafter. Active behaviours were recorded continuously. Postures were recorded every 2 min for 96 min and then every 6 min upto 180 min after treatment. Principal component analysis (PCA) and discriminant analysis (Minitab v12) were used to help determine the best single or combination of behavioural and physiological indices for allocating lambs to their correct treatment group.

Figure 1. PCA showing the relationship between lamb behaviour (60 min data) and the pain resulting from rubber ring castration and tail docking treatments of decreasing severity. Treatments: CTD bilateral castration and tail docking; C2 bilateral castration; C1 unilateral castration; C0 short scrotum castration; LA short scrotum castration with local anaesthetic; H handled control lambs.

The PCA showed that four postures involving lying with full extension of the hind limbs were associated with the most severe treatments, as were most of the active behaviours. Abnormal motion, standing still and lying with only partial extension of the hind legs were postures associated with treatments of intermediate severity. Vocalisation and trembling were also associated with these treatments. Lying on the sternum with all legs tucked in and standing with no abnormalities were postures associated with the LA and H lambs. Most lambs could be correctly allocated to their treatment groups when data collected for the first 60 min after treatment was analysed. Discriminant analysis showed that combining normal lying and standing postures allocated 62% of lambs to their correct treatment group, as did taking the sum of the active behaviours involving limb movements e.g. rolling, foot stamping, easing quarters (62%). A particular combination of postures and activities successfully allocated 78.6% of lambs to their correct treatment group. The inclusion of peak plasma cortisol values did not improve the allocation. The postures or activities were combined according to their close association within the PCA of the individual behaviours (Figures 1, 2).

Figure 2. PCA showing the relationship between lamb behaviour (60 min data) and the pain resulting from rubber ring castration and tail docking treatments of decreasing severity. Behaviours: V1 (head down) and V2 (head up) ventral lying with legs tucked in; Vtr V2 with trembling; Vg dog sitting; V3 ventral lying with partial extension of the hind leg; V4 as V3 with full extension of the hind leg. L1 (head up); L2 (head down); L3 (with rolling) lateral lying. S1 standing with no obvious abnormality; S2 standing with unsteadiness of gait; S3 standing with obvious abnormality including falling, walking on knees, stretching; SS1 standing still without eating or other obvious normal activity; SS2 standing still with obvious abnormalities e.g. trembling, hunched back, tail tucked between legs. EQ easing quarters; FSK foot stamping and kicking; HT head turning; Rljp rolling and jumping; Rst restlessness (getting up and down); TW tail wagging; Voc vocalisation.

It is concluded that an index of behaviours can permit the severity of acute pain from castration and tail docking with rubber rings to be assessed with greater than 70% accuracy. A similar index could be used in clinical conditions for recognising and assessing, with greater accuracy, unacceptable levels of pain of this type in lambs.

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