There is a growing trend towards the development of “welfare-friendly” management practices in production animals. Castration of piglets has gained considerable attention and there is growing pressure on the pork industry to develop management practices that address the pain associated with castration. The main objective of this experiment was to develop an effective, cost-effective and practical method of mitigating pain associated with castration in piglets. Two local anesthetic administration systems that would be easy to adopt in a commercial setting were examined; a needle free injection system (Acushot S) and a multidose injection syringe with a needle (Merial Pullet syringe). The project was divided into three separate experiments to examine the efficacy of the techniques and practical effects when implemented into a production system. Efficacy was measured using physiologic and behavioral measures of pain during administration of the local anesthetic and during castration. Behavioral measures of pain included using pain scores and vocalizations during anesthetic administration and castrations. Vocalizations have been shown to provide a valid measure of pain during castration in piglets. Piglets undergoing castration without anesthetic have higher frequency calls for longer periods of time than piglets that are handled but not castrated. Effect on processing times, cost implications, and perceptions of technical staff performing the processing procedures were evaluated.
In part 1 of the study, 30 3-4 day old male piglets were randomly assigned to receive a local anesthetic (lidocaine) injection into the testicles using a needle-free injector (ACUSHOT), a multidose injection syringe (NEEDLE), or no injection of lidocaine (SHAM). The time to achieve desensitization of the testicles was measured. Pain associated with castration was evaluated by measuring blood cortisol and lactate levels, eye and scrotal temperatures, and skin sensitivity over the castration site (pressure algometer). In part 2 of the study, 116, 2-3 day old male piglets were randomly assigned to receive one of the following; 1) localanesthetic and castration 2 minutes later (LIDO 2), 2) local anesthetic and castration 4 minutes later (LIDO 4), or 3) no anesthetic and castration after 2 minutes (CONT). In the local anesthetic groups, lidocaine was injected using a multidose needle injection syringe. Pain during anesthetic administration and during castration was measured using behavioral scoring (VAS) and vocalizations. Part 3 of the study examined implementation of the multidose needle injection syringe into routine piglet processing on the farm. Twenty-four litters of piglets were assigned by row to receive either local anesthesia or standard processing without anesthetic. The anesthetic was administered to all male piglets as they were removed from their pen and placed into a cart. Processing then occurred as follows: tail docking, antibiotic/iron injection, ear tattooing, and castration. Two to three processors, who routinely performed the processing on farm, worked together on each litter. The time to process each litter, time to process each row, males per litter, litter size, and minimum time from anesthetic administration to castration were measured. At the end of the study, individuals involved in the processing procedure completed a short questionnaire.
The major results found in the study included:
· The needle–free injection system (ACUSHOT) did not reliably produce anesthesia sufficient for castration. It was therefore removed from part 2 and 3 of the study.
· Injection of lidocaine with a needle (NEEDLE) was 92% effective within 2 minutes of administration.
· There was no significant difference in blood lactate, cortisol, pressure algometer readings, or eye and scrotal temperatures between any of the groups in part 1 of the study.
· Lidocaine administration significantly reduced pain during castration. Piglets receiving a local anesthetic struggled less and squealed at lower frequencies than piglets that did not receive an anesthetic. There was a beneficial effect of lidocaine both 2 and 4 minutes after administration.
· Lidocaine administration is less painful than castration without an anesthetic. The procedure of administering lidocaine resulted in piglets vocalizing less and at lower frequencies thanthe castration procedure itself.
· There was no significant difference in litter processing times when lidocaine administration was incorporated into the processing procedure. Although mean lidocaine administration time was 98 seconds, compared to 30 seconds in the control group, it took on average only 3 seconds longer to process each litter individually, or 34 seconds longer if continuously processing multiple pens in a row.
· Cost of treatment is relatively small. Implementation of lidocaine into routine processing would cost less than $1USD/litter. Currently there are no pain mitigation products in the US or Canada labeled for use in swine. Therefore, any pain medication used must be done under the direct supervision of a licensed veterinarian. In Canada veterinary approved products are available under prescription by a licensed veterinarian.
· Of the processors surveyed, all felt that the injection technique was easy and safe to perform, and if implemented on their farm, they could make it work within their system.
The results of this study support the implementation of local anesthetic administration into routine piglet processing. This study shows that local anesthesia reduces pain during castration with no impact on processing times, no major changes in the processing procedure, and with minimal additional cost. With increasing attention geared toward animal welfare and new regulations being implemented in other countries in regards to castration, this study provides a cheap, effective and practical method of mitigating pain during castration in piglets.
It is important to note however, that local anesthesia is effective at reducing pain during castration; it does not provide post-operative pain relief after castration has been performed (supported by our findings of no differences in cortisol, lactate, eye temperatures, and algometer readings in the 6 hours after castration). Therefore, this technique should be incorporated with the administration of an analgesic, such as meloxicam, in order to address the pain both during and after castration.
When considering implementation into a production setting, drug availability and appropriate drug use must also be considered. Currently there is no FDA labeled lidocaine product available for use in swine in the US. This means that an FDA human labeled product must be used extra-label under the supervision of a licensed veterinarian. In Canada, there are veterinary approved lidocaine products for use in swine however, they may also only be used under direction of a licensed veterinarian.
For more information please contact Dr. Erin Fierheller by email at [email protected].
