Effect of two methods and two anaesthetics for local anaesthesia of piglets during castration

BACKGROUND: Since January 2019, surgical castration of male piglets must be performed using local anaesthesia, if farmers deliver pigs to the primary exporting slaughterhouses according to the “Danish quality scheme”; a voluntary initiative taken by the Danish pig industry. The approved procedure for local anaesthesia in Denmark is a three-step injection method with procaine. A comparison of lidocaine and procaine with the same concentration and injection methods of local anaesthetics has not previously been studied. The purpose of this study was to investigate the effect of two injection methods and two local anaesthetics on piglets’ avoidance behaviour (vocalisation and resistance movements) as well as the time spent on the procedures. The study included 203 male piglets that were randomly assigned to one of five treatments: 1. Control: Sham-handling without injection of local anaesthesia, 2. Pro3: Procaine injection using a three-step method, 3. Pro2: Procaine injection using a two-step method, 4. Lid3: Lidocaine injection using a three-step method, 5. Lid2: Lidocaine injection using a two-step method. During injection of local anaesthesia and castration, vocalisation was measured using a decibel meter and resistance movements were registrated by video recordings. RESULTS: During castration, piglets treated with local anaesthesia showed significantly reduced vocalisation and resistance movements and time spent on castration was also significantly reduced compared to the control group. During injection of the local anaesthesia, the piglets had significantly increased vocalisation and resistance movements compared to the control group. Piglets injected with lidocaine had a significantly reduced resistance movement score and a tendency to reduced vocalisation compared to piglets injected with procaine. No differences in avoidance behaviour were found between the injection methods. CONCLUSIONS: The use of local anaesthesia, irrespective of the method and local anaesthetic, was effective in reducing vocalisation and resistance movements during surgery as well as the time spent on castration.