[Pain and distress response of suckling piglets to injection and castration under local anaesthesia with procaine and licocaine - Part 2: Defence behaviour, catecholamines, coordination of movements].

OBJECTIVE: Comparison of the effectiveness of local anaesthesia (LA) in piglet castration with the combination of scrotal and inguinal application of procaine 2 % and lidocaine 5 % to the intratesticular application of lidocaine 1 % using following parameters: adrenaline (A), noradrenaline (NA), defensive movements and coordinated movement patterns.
MATERIAL AND METHODS: In 2 substudies 232 male suckling piglets (3-6 days of age) were randomly allocated to study groups. In groups L5 and group P2 lidocaine 5 % and procaine 2 % was applied inguinally and scrotally, respectively, while piglets of groups H (handling) and K (castration without local anaesthesia) were only fixated as for an injection. In group L1 lidocaine 1 % was injected intratesticularly. After 30 min piglets were were castrated, whereas animals of group H were again only fixated. In substudy 1 (n = 112) blood samples were taken to determine the concentration of catecholamines after castration. During injection and castration defensive movements were judged. In substudy 2 (n = 120) piglets completed a chute to document the individual stress level.
RESULTS: Groups H and L1 demonstrated significantly less defensive movements during fixation for injection/injection compared to the other study groups (p ≤ 0.05). After the injection piglets of group P2 had significantly more difficulties in the chute and needed > 50 % more time to complete the course. In all study groups defensive movements during castration were the highest at the moment of severing the spermal cord. Group K obtained the highest possible rating of 8 and differed significantly from the other groups as well as when cutting the skin (p ≤ 0.05). Both the concentration of A and NA significantly rose in all groups. The increase in A and NA was significantly higher in group 2, as well as the increase in NA in group K, both in comparison to the other study groups (p ≤ 0.05).
CONCLUSION: None of the applied techniques for local anaesthesia achieved a complete elimination of pain during castration of suckling piglets. The behaviour analysis indicated an altogether higher distress for P2. After castration, this injection led to a neuroendocrine pain reaction that was comparable to or higher than that of group K. In both lidocaine groups (L1, L5) the pain reaction after castration tended to be lower. These results provide approaches to apply longer acting LA with a higher analgesic potency in an appropriate dosage and with an appropriate method of application. © Georg Thieme Verlag KG Stuttgart · New York.