Date Full Report Received03/04/2019
Date Abstract Report Received03/04/2019
InvestigationInstitution: North Carolina State University
Primary Investigator: Dr. Kristen Messenger
Co-Investigators: Glen Almond, Ronald Baynes, Emma Nixon, Alexandra Carlson, Liliana Hernandez, Patricia Routh
Funded ByNational Pork Board
The provision of pain alleviation for painful procedures in piglets, including castration and tail-docking, is required by law in the European Union and will likely become required in the USA. Nonsteroidal anti-inflammatory drugs (NSAIDs) are currently being used in the EU and Canada for this purpose. However, there is conflicting research on which NSAID is the most effective and appropriate for this application, and currently there are no pain medications approved for use in swine in the US. This research examined and compared the effects of 3 different NSAIDs on pain and inflammation following piglet processing (castration and tail-docking).
At 4 days-of-age, male Yorkshire x Landrace piglets were removed from the sow and IV catheters and interstitial probes were placed. At 6 days-of-age, piglets were assigned to one of five treatment groups (saline sham [SAL SHAM], 0.1 mL saline and no processing; saline castration [SAL CAST], 0.1 mL saline and processed; Meloxicam treatment [MLX], 0.4 mg/kg meloxicam and processed; Flunixin treatment [FLU], 2.2 mg/kg flunixin meglumine and processed; or Ketoprofen treatment [KETO], 3 mg/kg ketoprofen and processed). All NSAIDs and saline were administered intramuscularly, two hours before processing. Pigs were sampled and observed up to 48 hours post-dose. Pain assessments included a behavior score, piglet grimace score, thermal imaging, and activity monitoring.
Flunixin was present in both the blood and interstitial fluid for longer than either meloxicam or ketoprofen in our study, and also had the longest-lasting effects of decreasing inflammation based on the measurement of prostaglandin E2. The dose was given 2 hours prior to processing, which was ideal as the interstitial fluid concentrations peaked between 2-4 hours; these tissue concentrations are more likely to be indicative of the effective concentrations since it reflects biologically active drug located at the site of action.
When comparing the SAL CAST and SAL SHAM groups, castration notably increased cortisol levels immediately at the time of processing in all groups. Treatment with flunixin lessened the increase in cortisol, when compared with the SAL CAST group. All the NSAIDs decreased prostaglandin E2 levels in interstitial fluid (i.e., tissues) when compared to the SAL CAST group, however only flunixin was able to maintain that inhibition beyond 24 h post-dose.
Overall, meloxicam was the least effective NSAID when examining the behavior and grimace scores beyond 6 h post-dose. At the time of processing, all the NSAID treated groups had increased pain behaviors and increased pain scores. This may have been noted because the piglets were more active, making the active pain-related behaviors more obvious to the observers (e.g. scratching at castration site), compared to the SAL CAST group which showed more inactive behaviors (e.g. laying still and protecting the castrated site). Activity levels, obtained via Actical® monitoring, were also decreased in the SAL CAST and MLX piglets following processing. This was likely related to the reduced number of active pain-related behaviors.
In conclusion, this study found that the administration of NSAIDs 2 hours prior to castration and tail docking had a positive impact on pain alleviation in piglets, with flunixin demonstrating superiority compared with ketoprofen and meloxicam, and meloxicam being the least efficacious of the three treatments at the doses studied. Management strategies that include the administration of flunixin to reduce pain associated with processing will improve piglet health and welfare in the United States.