Effects of acute pain reduction methods on the chronic inflammatory lesions and behaviour of lambs castrated and tail docked with rubber rings at less than two days of age

Lesions were produced by castration and tail docking of two-day-old Dorset- cross lambs with elastrator rings with (RRla) and without (RR) local anaest hetic or after destruction of the innervation by crushing close to the ring (Brr). The lesions were monitored twice weekly for six weeks and the behav iour of handled controls (H), RR and RRla lambs was recorded for two 3 h pe riods 10, 20, 31 and 41 days after treatment. There was no significant effect of castration and tail docking, with or. wi thout pain reduction methods, on daily liveweight gain. In die Err lambs, t he dead tails were cast 19 days earlier than from RR and RRla lambs. The ti me taken for the scrotal lesion to reach maximum severity was halved in Err and RRla lambs, although the maximum severity of the lesion was unaffected by the methods of pain reduction. During the four 6 h behavioural observat ion periods, RR lambs showed a significant increase in the mean (+/-sd) fre quency of foot stamping (RR13 +/- 13; H2 +/- 2.5), tail wagging (61 +/- 26; 15.6), head turning to the scrotum and inside hind-leg (12 +/- 10; 1 +/- 1 ). Less abnormal behaviour was found after RRla than after RR treatment. Th is unexpected finding may be evidence of long-lasting increases in pain sen sitivity after an episode of intense acute pain in young animals. (C) 3000 Harcourt Publishers Ltd.