Analgesia and/or anaesthesia during piglet castration–part I: efficacy of farm protocols in pain management

Pain alleviation associated with surgical castration of piglets is a debated welfare issue. The present study compares the effect of different protocols involving analgesia and/or anaesthesia or sedation suitable under field conditions, with the aim to alleviate pain due to castration in piglets. A randomised within-litter design, with 50 replicates, compared 7 treatments applied 10min before castration: HAND: positive control, handling only; CTRL: negative control, physiological saline, i.m.; MEL: meloxicam, i.m.; AZA: azaperone, i.m.; PROC: local anaesthesia with procaine and adrenaline, subcutaneously; AZA-MEL: joint administration of azaperone and meloxicam; PROCMEL: procaine and meloxicam. Efficacy of pain relief was assessed during a 180 min period after castration by serum cortisol and glycaemia, algometry and behaviour. CTRL, AZA, PROC and AZA-MEL piglets showed an increase in cortisol concentration 60min after castration compared to HAND. Both groups with azaperone (AZA and AZA-MEL) developed concentrations even higher than CTRL (p<.001). HAND treatment showed cortisol levels comparable only to MEL and PROC-MEL (p>.05). CRTL and PROC piglets reacted to the algometer at an average lower pressure than HAND (p¼.03), differently to the other treatments that showed similar skin sensitivity to HAND (p>.05). No differences in glycaemia and behaviour were observed among treatments. The results suggest that using meloxicam alone might offer a promising option in reducing the expression of pain-related parameters in piglets after surgical castration, however, it appears more efficient when used alone than in association with the anaesthetic agents tested. Procaine administered alone and azaperone seems unsuited to the purpose considered.