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How to achieve the best effect of local anaesthesia when castrating piglets?

As from 1 January 2018, Danish farmers were given the opportunity to anaesthetize their piglets prior to surgical castration. The use of local anaesthesia prior to castration may seem an advantage to the piglets, but administration of the aesthetic drug is not painless, it does not cover the entire painful period post-castration, and only few drugs are licensed for this use in Denmark. Therefore, it is important to identify the advantages and disadvantages of different anaesthetics and their respective use. A group of researchers from Aarhus University will examine this particular area.

2019.11.17 | Camilla Mathiesen

[Translate to English:] Foto: Mathilde P. Coutant, AU

Photo: Mathilde P. Coutant, AU

Today, almost all Danish male piglets are castrated between the age of 2 and 7 days in order to avoid boar taint in the meat. Before 2018, castration was performed without the use of anaesthesia. As from 1 January 2018 – and having completed a training course – Danish farmers were given the opportunity to anaesthetize their piglets prior to castration; and as from January 2019 a general industry agreement requires that piglets are anaesthetized prior to the procedure. As a part of Aarhus University’s agreement with the Ministry of Environment and Food of Denmark on science-based policy support, The Danish Veterinary and Food Administration has requested researchers from the university to examine if the method recommended today will provide the best possible pain relief, or whether it may be adjusted to improve pain relief and welfare.

Less pain

Working with local anaesthetics is new to Danish farmers. They are familiar with vaccinations and injections in case of diseases, but these are simpler procedures compared to administering local anaesthetics to specific parts of the body. In order for famers to administer local anaesthesia, The Danish Veterinary and Food Administration requires that they complete a training course in a method already used in Sweden, and now recommended in Denmark: the anaesthetic is administered in skin, testicle and at the spermatic cord. Post Doc Hanne Kongsted, Department of Animal Science at Aarhus University, explains that the researchers will study the entire castration procedure:

- We apply a holistic approach. We know that it hurts, when you castrate a pig without anaesthesia. However, applying anaesthesia introduces other painful and stressful events to the pigs. Nobody wants to introduce a method that implies the same or potentially even more severe pain and adverse effects on the welfare, than castration without anaesthetics. Overall, we aim to describe the least painful and stressful method in order to improve the welfare of the pigs.

Three methods are tested

Based on interviews with farmers, veterinarians and representatives from the pharmaceutical companies producing the drugs licensed for this purpose in Denmark, the researchers have so far identified three different methods to be examined:

”The Swedish method” (described above), which is officially recommended, a more simple procedure where the anaesthetic is injected only into the testicle, and finally a method where the anaesthetic is injected into the testicle and the skin.

Another aspect of the study is the interval from administration of the anaesthetic and until the castration procedure begins. Today, the recommended interval is 5 minutes; however, there is no documentation as to this interval – how many minutes are sufficient and how long can you wait. This knowledge is important in practice, as the farmer will often have many piglets to castrate on a given day.

Anesthesia makes a difference

Interviews with farmers and veterinarians experienced with applying anaesthesia prior to castration suggest that anesthesia has a positive effect for the pig when castrated. However, a number of unresolved questions remain. For instance, Danish farmers are required to use anesthetics based on the active drug procaine, while most studies in the literature were carried out using lidocaine.

- The professionals that we have interviewed, and who have practical experiences with local anaesthesia and castration, unequivocally state that anaesthesia does make a positive difference. The piglets seem calmer; and they do not scream or move quite as much. We hope to identify a method that is more simple than the current practice, and with a reduced risk of mistakes. Farmers are busy, and if it would be possible to apply only one injection and know that the piglet does not feel pain, this would be a great relief in the herds, Hanne Kongsted explains.

In Denmark, two different types of anaesthetics have been approved for local anaesthesia in piglets. The existing guideline for anaesthesia does not consider the difference. The study will establish whether there is any reason to make separate recommendations for e.g. the timing of incision and the volume of drug used. The recommended “Swedish method” is performed in Sweden using lidocaine, a drug not approved for use in Denmark. According to the researchers’ interviews with professionals, who have experiences with both procaine and lidocaine, the effect of lidocaine is better.

Experimental study initiated

In order to gain knowledge about the applicability of the different methods, experimental studies will be carried out during the next 3 years. The photo below illustrates the preliminary studies in the facilities at Aarhus University, Foulum. 

Read more – in Danish - in the DCA report: Hvordan lokalbedøver man pattegrise inden kastration?

For further information, please contact:

Post doc at Department of Animal Science: Hanne Kongsted E-mail: hanne.kongsted@anis.au.dk Mobile: +45 9350 8454

Senior Researcher at Department of Animal Science: Mette S. Herskin E-mail: mettes.herskin@anis.au.dk Mobile: +45 5050 2969 

DCA, Anis, Pigs