[Pain and distress responses of suckling piglets to injection and castration under local anaesthesia with procaine and lidocaine - Part 1: Cortisol, chromogranin A, wound healing, weights, losses].

OBJECTIVE: Comparison of the effectiveness of local anaesthesia (LA) in piglet castration by procaine 2 % and lidocaine 5 % both through combined inguinal and scrotal application as well as by intratesticular application of lidocaine 1 %. The parameters used were serum cortisol and chromogranin A (CgA) concentrations as well as wound healing, body weight and animal losses.
MATERIAL AND METHODS: In 2 substudies, a total of 232 male piglets aged 3-6 days were included. Substudy 1 (112 piglets): Group H: fixation of piglets as for an injection; group L5: inguinal and scrotal injection of lidocaine 5 %; group P2: inguinal and scrotal injection of procaine 2 %; group L1: intratesticular injection of lidocaine 1 %. In all the groups, blood samples were taken 45 minutes before and 30 minutes post-injection (p. i.). Substudy 2 (120 piglets): Group H: handling only as for an injection and castration; group K: handling as for an injection and castration without LA after 30 minutes. Groups L5, P2 and L1: management as in substudy 1 and castration after 30 minutes. Blood samples were taken 75 minutes before as well as 30, 60 and 240 minutes post-castration (p. c.). The evaluated parameters were serum cortisol and CgA concentrations, wound healing, body weight and piglet losses.
RESULTS: Substudy 1: The elevation of the cortisol and CgA concentrations in group P2 p. i. were significantly higher than in the other groups. The mean total cortisol concentration of group P2 p. i. was significantly higher than those of the other groups. Substudy 2: At 30 minutes p. c., all the groups displayed a significant increase in the cortisol concentration compared to group H. In group P2, the highest total cortisol concentration was measured 60 minutes p. c. and the elevation of the cortisol level was significantly higher than in the other groups. In group L1, a significantly greater increase in the CgA level was observed at 60 minutes p. c. when compared to the other groups. Regarding wound healing, body weight and losses, there were no significant differences between the groups.
CONCLUSION: The combined inguinal and scrotal injection of procaine 2 % induced a greater neuroendocrine stress response than the inguinal and scrotal injection of lidocaine 5 % and the intratesticular injection of lidocaine 1 %. LA using procaine 2 %, lidocaine 5 % or lidocaine 1 % did not completely eliminate pain during castration. Castration under LA with procaine 2 % induced a greater pain reaction than castration without LA. Both groups castrated with LA using lidocaine (L1, L5) tended to display lower pain responses after castration than group K. On the basis of the findings of this study, other local anaesthetics that have a stronger effect could be further investigated according to their pain-killing effects in an appropriate application route. © Georg Thieme Verlag KG Stuttgart · New York.