Administration of local anesthesia prior to castration and dehorning is legislated in several European countries, however, there are currently no analgesic drugs specifically approved for pain relief in livestock by the U.S Food and Drug Administration (FDA), says Hans Coetzee, BVSc, Cert CHP, PhD Kansas State University.

FDA Guidance Document 123 for the development of effectiveness data for non-steroidal anti-inflammatory drugs (NSAIDs) states that “validated methods of pain assessment must be used in order for a drug to be indicated for pain relief in the target species.”

Coetzee explains that the identification and validation of robust, repeatable pain measurements is therefore fundamental for the development and approval of effective analgesic drug regimens for use in livestock. “Research to address our limited knowledge in this area is therefore essential to formulating science-based recommendations.”

Methods that have been used to assess pain in cattle after procedures such as castration include behavior, production parameters and cortisol response. However, these methods are imperfect indicators of measurable pain responses.

Newer methods of measuring pain include measuring Substance P (a neuropeptide present in areas of the
neuroaxis involved in the integration of pain, stress and anxiety) and using tools such as accelerometers (to measure standing, walking, lying time), radar speed cameras (to measure the speed of cattle exiting the chute) and EEGs (to quantify some of the changes in brain activity associated with pain following castration).

Coetzee notes that the results of a castration study with Holstein calves showed that EEG is a sensitive and specific measure of changes in brain electrical behavior associated with castration. One of the major benefits of using this technology is that this is readily accepted by consumers because it is widely used in the medical field, he says. This tool would thus be useful to determine the effect of age and method of castration and therefore formulating science-based animal welfare regulations.

Pain and multiple procedures

The preliminary results of a USDA-funded study conducted by Ruby Mosher, DVM, MBA, a graduate student at Kansas State University, suggest that calves experiencing dehorning alone or dehorning and castration at the same time have lower average daily weight gains over seven days following the procedure compared with calves experiencing only castration.

In order to address questions about the optimal timing and method of castration, Kansas State’s Lucy Bergamasco, DVM, PhD, will be applying her expertise in electrophysiology to the questions of animal welfare which are associated with routine husbandry of domestic livestock. In an important series of upcoming studies, Bergamasco’s expertise will be combined with that of other researchers in the study group to examine the effect of timing and age at castration on EEG responses in calves.