Topical anaesthesia reduces sensitivity of castration wounds in neonatal piglets.

The aim of this study was to do determine the efficacy of the topical anaesthetic Tri-Solfen® in the amelioration of the pain of castration in piglets. The trial was conducted over a three day period, and blocked across six litters with 12 piglets treated on days one and two, and 16 on day three. The piglets were randomly allocated by weight and litter to 1 of 4 treatment groups: (i) sham castration (SHAM; n = 10); (ii) surgical castration with no anaesthetic intervention (CAST; n = 10); (iii) surgical castration with post-operative topical anaesthesia (TRI; n = 10); (iv) surgical castration with a pre-operative intra-testicular lignocaine hydrochloride injection (LIG; n = 10). Wound sensitivity testing involved von Frey monofilaments of weights 4g and 300g, and an 18 gauge needle, used to stimulate the wound and surrounding skin respectively, at various pre-determined sites. Neonatal piglets receiving topical anaesthesia (Tri-Solfen®) spray into castration wounds had significantly lower wound sensitivity responses for up to 4h, compared to those castrated following intra-testicular lignocaine injection or those with no treatment. The use of topical anaesthetic is suggested as a practical and affordable method of improving piglet welfare during castration.