Analgesia and food animals

The alarm buzzed at 4am. I hit the “off” button and tried to go back to sleep. Then I remembered that it was my turn to watch the new calves that had been born the day before. Hurriedly, I brushed my hair with one hand and washed my face with the other. Still groggy, I ran into the barn and found my charges snoring lightly on a bed of hay. Seeing that all was well, I plopped down in the corner of the stall.

I was awakened by a blast of sunlight as one of the farm hands opened the barn doors. Squinting, I could see that Dr Coleman had arrived. I ran out to greet him and asked if I could assist with his medical tasks. Without looking up, he grumbled, “How about helping with the calves?” Not knowing what that would entail, I agreed and followed him back into the barn.

We stopped at a pen with six young bull calves. “Do you want me to feed them?” I asked. “No, I want you to castrate them.” Before I could respond, he began to instruct me how to spray, slit, pull, cut, and then quickly get out of the way.

“Um, what do I give them for pain?” I asked. “They don’t need anything,” Dr Coleman replied. “It’s quick and doesn’t hurt much.” But for many nights following that gruesome day, I was haunted by the bellowing of those young calves.

I recently wondered whether current practice was more humane. I was troubled by what I found. As reported by Virginia Fajt, DVM, PhD, analgesic drugs are not administered to 70% of calves castrated before six months of age.1 The most commonly used extra-label drugs include lidocaine, xylazine, flunixin meglumine, butorphanol, and ketamine. Depending on the age of the calf, these interventions are usually effective, according to Fred DeGraves, DVM, PhD, Assistant Professor of Animal Science at Western Kentucky University. However, more effective extended pain control agents are needed.

How do animals experience pain? According to Vince Molony, BVSc, PhD, “animal pain is an aversive sensory and emotional experience representing awareness by the animal of damage or threat to the integrity of its tissues.”2 A cow in pain may be less mobile, have a decreased appetite, put its head against the wall, and appear to be constantly chewing. One bovine practitioner told me that “. . . cows are very stoic… (however, that’s) no excuse. It’s easier to treat pain before it starts. Just like with people.”

The American Veterinary Medical Association’s Animal Welfare Division supports pain alleviation in its policy, revised in 2011: “Drugs, techniques, or husbandry methods should be used to prevent, minimize, and relieve pain in animals experiencing or expected to experience pain.” If efficacy is not an issue for the relatively small proportion of calves castrated, are drugs specifically targeted at bovine pain actually required? Many would argue that the economics do not support further development of such drugs since extra-label drugs are available.

Moreover, the development of specific bovine pain management drugs may be hampered by the inability to measure efficacy. Carmen Stamper, DVM, wrote in FDA Veterinarian (2008, No. VI, page 8): “For an analgesic to be FDA-approved, it must undergo studies showing it is safe and effective. However, because valid methods to measure food animal pain are unavailable, it is difficult to design those studies.”

In 2009, a Kansas State University team led by J. Hans Coetzee, BVSc, received grant funding from the US Department of Agriculture to develop such a tool. “Coetzee said his model will help the FDA evaluate drugs for cattle by knowing how well they work and to recommend proper dosing.”3 This research continues at KSU under Brad White, DVM, whose team is studying accelerometer data to monitor behavior and potentially assess pain. Dr. White expects to publish additional results later this year.

It appears that opinions regarding pain management in production animals remain less definite than they are for companion animals. As more data become available, though, that disparity may dissipate . . . as it should.

References

1Analgesic drug administration and attitudes about analgesia in cattle among bovine practitioners in the United State,” Journal of the American Veterinary Medical Association, 238(6):755.
2Assessment of Acute Pain in Farm Animals Using Behavioral and Physiological Measurements,” Journal of Animal Science 75(1):266.
3Kansas State University news release, February 17, 2009, “K-State Veterinary Researchers Developing Model That Will Make it Easier for Producers, Veterinarians to Make Cattle More Comfortable.”