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Effects of ethyl alcohol analgesia on pig behavior during castration

Ferranti, Emily Marsh
Newborn piglets born on commercial farms undergo various procedures in their first days of life. These procedures can include tail docking, various injections, and castration. One of the most common and invasive is castration. Boar piglets are castrated to prevent unwanted sexual behavior, aggression, and boar taint. Boar taint occurs when intact males that have reached sexual maturity are slaughtered, causing an offensive odor and taste (Sutherland, 2015). Castration invokes a pain response, but it is most often performed without any anesthesia or analgesia. This is mostly due to the lack of a readily available and inexpensive analgesia. Lidocaine is a common analgesic that is expensive and must be administered by a veterinarian. Castration without pain relievers raises welfare concerns and it would be beneficial to find an inexpensive and readily available alternative.
This study explores ethyl alcohol as a possible alternative. When injected into an area, ethyl alcohol performs alcohol neurolysis. This causes the demyelination of the neurons, leading to pain relief. In this experiment, boar piglets from 14 litters were assigned a treatment group. They were either injected with 1mL of saline solution (CON), injected with 1mL of ethyl alcohol (ETOH), or were injected with 1mL of lidocaine (LID). A gilt from each litter served as a handling control (SHAM). Each piglet was injected with their perspective treatment at 3 days of age. They were then subsequently castrated at 14 days of age. The SHAM was handled the same way as the boar piglets, but no incision was made.
The piglets were recorded for 24 hours/day beginning one day prior to treatment and ending 14 days post-castration. The videos were used to evaluate the behavior of each piglet. The frequency of certain behaviors listed in an ethogram were recorded. The averages of each behavior performed by each treatment were analyzed for statistical significance.
Overall, it was found that ethyl alcohol has similar effects as lidocaine. The ethyl alcohol and lidocaine appeared to cause some discomfort when injected as those treatments displayed higher incidences of rump scratching (P < 0.05) and stiffness. This is to be expected as the CON was only injected with saline and the SHAM was not injected at all.
The frequencies of behaviors performed by the ETOH and LID post-castration were very similar. Ethyl alcohol appears to have the same effect on pain as lidocaine. Both significantly decreased the instances of pain related behaviors compared to the CON.
More research needs to be conducted on ethyl alcohol as a possible analgesia for piglet castration. However, in this study, it does seem to reduce pain caused by castration and does so in a manner comparable to that of lidocaine. Based on this observation, ethyl alcohol is a good candidate for an inexpensive and effective analgesia.