Effects of an oral dose of acetyl salicylate at tail docking on the behaviour of lambs aged three to six weeks

To investigate a practical method of providing analgesia for docking of lam bs' tails, the effectiveness of an oral dose of aspirin (acetyl salicylate) in reducing discomfort behaviour immediately following application of elas trator rings, was evaluated. The study involved a pilot trial and an experi ment, both using Romney crossbred lambs aged 3-6 weeks accompanied by their mothers in a group pen, with behaviour recorded on videotape. In the pilot trial, lambs were manually restrained, an elastrator ring was applied, the n lambs were given either an oral dose (26 mg/kg) of aspirin dissolved in w ater (Treatment RA, n = 5 lambs) or an oral dose of water (Treatment R, n = 4 lambs), and released. RA lambs changed posture between sternal recumbenc y and standing less frequently than R lambs, significantly so from 10 to 20 min post-treatment (11 times for RA, compared with 28% (S.E.D. 6.6%) for R lambs). In the experiment, 56 lambs were given one of two docking treatmen ts (either RA: application of an elastrator ring plus the same aspirin trea tment as in the pilot trial, or R: application of the ring plus water), or one of two control treatments (CA: restraint plus aspirin; or C: restraint plus water). During the hour after treatment, docking was associated with d ifferences in over three quarters of 52 postures and activities used to des cribe behaviour (P < 0.05), and marked changes over time in the postures/ac tivities affected were observed. Differences were evident within 5 min and some were still apparent at 60 min posttreatment. When postures and activit ies were designated as 'normal' or 'abnormal' (typical of docked lambs), ov er the total hours of observation the mean frequency of abnormal postures w as 3.5% for control lambs and 22.6% (S.E.D. 1.64%) for docked lambs, and th e mean frequency of abnormal activities was 5.2% for control lambs and 19.3 % (S.E.D. 1.40%) for docked lambs. Provision of aspirin to docked lambs was associated with similar levels to those seen in control lambs for two acti vities but was also associated with increased levels of some activities/pos tures (P < 0.05). These effects were minor compared with the effects of doc king and there was no indication of effective analgesia. Thus, when elastra tor tail docking rings were applied, behavioural effects indicative of pain were observed immediately and did not subside fully within 1 h. Despite in dications in the pilot trial of an analgesic effect of aspirin, further exp erimentation did not substantiate this effect. (C) 2001 Elsevier Science B. V. All rights reserved.