Reducing the Pain of Band Castration

Background

Castration is painful regardless of how it is done, but the nature of the pain depends on the method used. The pain of surgical castration is most acute for a few hours and goes away after a few days, so there is not much chronic pain. Commercially available pain medications can significantly help alleviate that kind of pain. Band castration hurts less acutely, but the chronic pain lasts a lot longer, particularly when the scrotum sloughs off weeks later. Current pain medications do not last long enough to address that kind of chronic pain. Alberta Veterinary Laboratories has developed castration bands that are impregnated with a slow-release anesthetic (lidocaine). The band has been shown to release lidocaine for 7 days, but it needs to work for much longer before it can claim to effectively relieve the pain of band castration.

Objectives

• Determine the efficacy of a slow-released anesthetic at mitigating the acute and chronic indicators of pain measured in castrated beef calves, including physiology, behaviour, and weight gain,
• Characterize the signs of pain and welfare expressed by calves at those two industry-relevant ages when exposed to an extended-term delivery of topical anesthesia, and
• Develop a standardized pain evaluation protocol including the use a combination of behavioural and physiological traits indicative of pain and discomfort to facilitate the development and registration of future pain mitigation tools.

What they Did

A total of 96 calves were castrated either at one- or five-months of age. At each age, calves were divided into three castration protocols: regular bands with no pain control, regular bands with anesthetic injected into the scrotum, and the new bands with slow-release anesthetic. Many pain-related behaviors, physiological responses and growth measurements were taken at the time of castration and in the following hours, days and weeks. An additional study with 31 bull calves was conducted to measure anesthetic levels in the scrotal tissue over time.

What They Learned

Physiological and behavioural indicators of pain were detected at the time of castration, up to 240 minutes after castration, and during the time the testicles sloughed off for both 1- and 5-month-old bull calves, highlighting the time when pain mitigation should be implemented.

We found limited differences between the two lidocaine treatment protocols, administered either injected into the spermatic cord or topically applied through the band:

• In 1-month-old calves, and compared to unmedicated calves (control group), injected lidocaine reduced VAS during castration, and lidocaine bands tended to have lower haptoglobin concentrations up until 56 days after the procedure.
• In 5-month-old calves, injected lidocaine reduced saliva cortisol concentrations 60 and 120 min after castration compared to unmedicated calves.

Lidocaine was effective at mitigating some but not all pain associated with band castration in 1- and 5-month-old bull calves. A multimodal pain mitigation strategy, where the use of lidocaine is combined with other pain control drugs, such as sedatives or anti-inflammatory drugs may control pain more effectively.

The study investigating the effective tissue concentrations of lidocaine identified that the use of traditional pain control (a ring block with injected lidocaine) was effective in mitigating the pain associated with castration for up to 60 min post-procedure.

The use of a lidocaine-loaded bands (LLB) led to tissue concentrations of lidocaine approaching an effective dose by 2 h and meeting or exceeding the peak concentration in the tissue by 72 h, an remaining at that level for at least 28 days, indicating that local anesthesia is likely provided by LLBs.

What It Means

The behavioural and physiological parameters assessed showed expected results on the effects of band castrating calves, while LBAND calves tended to have lower concentrations of haptoglobin compared to REG+L and REG treatments only in 1-month old calves, suggesting a lower level of chronic pain at that age.

Results show that bands impregnated with lidocaine yielded tissue levels of lidocaine that approached an effective dose and peaked at 2- and 72-hours following application, respectively, and remained above those levels for at least 28 days after application.

Results from the three studies suggest that lidocaine-loaded elastration bands succeeded at releasing lidocaine into the scrotal tissue, but with moderate effects on reducing acute and chronic signs of pain due to band castration.