Topical anaesthesia alleviates short-term pain of castration and tail docking in lambs.
OBJECTIVE
To investigate the effect of a topical anaesthetic formulation on pain alleviation, wound healing and systemic levels of local anaesthetic actives in lambs undergoing castration and tail docking.


METHODS
Three placebo-controlled and/or randomised experiments were conducted using three groups of Merino lambs (n = 62, 68 and 19) undergoing routine castration and tail docking.


METHODS
Surgical castration, with either surgical or hot-iron tail docking, was performed with and without the application of topical anaesthetic (Tri-Solfen) or placebo. The effects of this procedure were compared with those of rubber ring castration and tail docking, and of the handled but unmarked controls. Wound pain was assessed using calibrated Von-Frey monofilaments over a 4-h period, pain-related behaviour was assessed over 5 h, wound healing was assessed at 14 and 28 days, and the plasma levels of lignocaine and bupivacaine were determined.


RESULTS
Rapid and up to 4 h primary hyperalgesia developed following surgical castration and tail docking in the untreated and placebo-treated lambs. It was absent in the castration wounds, and significantly reduced in the tail-docking wounds, of the treated lambs. Hot-iron docking was associated with mild and transient secondary hyperalgesia, which was abolished by the topical anaesthesia. There was a significant reduction in pain-related behaviours in treated lambs, which were not significantly different in their behaviour to the sham-operation handled controls. Plasma lignocaine and bupivacaine levels were below the toxic thresholds in all tested lambs.


CONCLUSIONS
Topical anaesthesia alleviates wound pain and significantly reduces pain-related behaviours in lambs undergoing surgical castration plus surgical or hot-iron tail docking, without a negative effect on wound healing or a risk of systemic toxicity.
Lomax
S
S
Faculty of Veterinary Science, University of Sydney, PMB 3, Camden, New South Wales 2570, Australia. pwindsor@camden.usyd.edu.au
Dickson
H
H
Sheil
M
M
Windsor
P A
PA
D000772:Anesthesia, Local / Q000662:veterinary*; D000827:Animal Welfare; D000818:Animals; D000831:Animals, Newborn; D001522:Behavior, Animal; D002045:Bupivacaine / Q000097:blood; D002369:Castration / Q000379:methods / Q000662:veterinary*; D005260:Female; D008012:Lidocaine / Q000097:blood; D008297:Male; D010146:Pain / Q000517:prevention & control / Q000662:veterinary*; D011897:Random Allocation; D012756:Sheep / Q000097:blood / Q000502:physiology / Q000601:surgery*; D013623:Tail / Q000601:surgery*; D014945:Wound Healing
D008012:Lidocaine; D002045:Bupivacaine