New research shows calves experience pain for 9 weeks after disbudding

Sarah Adcock and Cassandra Tucker for Progressive Dairyman Published on 08 November 2018

PHOTO: A pressure algometer measures how much force is applied at the edge of the disbudding wound. Photo provided by Sarah Adcock and Cassandra Tucker.

If you've experienced a severe burn, you'll know all too well that the pain doesn't disappear overnight. In fact, it can get worse before it gets better. When it comes to hot-iron disbudding, calves may be in a similar boat.

Through research, we have found pain not only occurs immediately after disbudding, it lasts throughout the nine weeks it takes for a new layer of skin to form (see Figure 1).

Assessing pain levels

How do we know when a calf is in pain? In the wild, as a prey animal, it would be in the calf's best interest to hide signs of pain. Although calves seem to bounce back and often feed easily after disbudding, there are changes that are more difficult to see. Studies that have carefully tracked changes in behavior and physiology have found signs of pain, such as increased ear flicking, head shaking and head rubbing. We also see increased levels of stress hormones in the 24 hours after disbudding. We know these are signs of pain because calves given pain relief do not show these same changes.

Another way to assess pain is to use a device called a pressure algometer. Algometers are used with human and veterinary medicine to measure a patient's level of pain. We touch the tip of the algometer to the site of the injury and apply increasing pressure until the calf moves away. If she moves away very quickly, with little pressure from the device, this tells us there is pain.

Using a pressure algometer, we measured how quickly calves responded when we pressed on their wounds in the weeks after hot-iron disbudding. During the nine-week healing process, calves responded to the algometer sooner than after they had healed, telling us that the wounds were painful throughout this time. We don't know whether the wounds are painful when they aren't being touched, and we are currently working on answering this question.

Methods for reducing pain

Our findings tell us that current methods for managing disbudding pain are not enough. The American and Canadian Veterinary Medical Associations recommend a combination of local anesthetic and a nonsteroidal anti-inflammatory drug (NSAID) for disbudding. We gave our calves a cornual nerve block of 5 milliliters of 2 percent lidocaine hydrochloride on each side of the head and 1 milligram per kilogram oral meloxicam. These drugs, although highly effective, are limited to controlling pain in the hours to days after disbudding. Lidocaine stops the pain for up to two hours, while meloxicam, one of the longest-acting NSAIDs, helps with pain for up to two days. That leaves several weeks of untreated pain. Unfortunately, there are no drugs for producers to manage pain over several weeks. However, we may be able to reduce the amount of time the calf is in pain by helping her heal faster.

To do this, we looked at whether disbudding near birth would speed up healing. We used a 1/4-inch iron tip to disbud 3-day-old calves and a 1/2-inch tip on 35-day-old calves. We expected wounds would heal faster in the younger calves since less tissue was damaged. Instead, we found that disbudding age did not matter. The wounds took nine weeks to heal and were painful throughout healing regardless of age.

We also looked at whether the type of iron affected healing time. We compared healing after disbudding 4- to 10-day-old calves with two commercially available irons: the Rhinehart X50A (1/4-inch tip) and the Portasol Dehorner III (5/8-inch tip). Even though the irons produce different burns (see Figure 2), we found that their healing times were similar.

People vary in how they use disbudding irons. Hot-iron disbudding can be performed by leaving the horn bud inside the burned copper ring intact, as we do in our experiments, or by flicking it out using the iron. Bud-in and bud-out methods result in different wounds and, maybe, different healing times. The Portasol can also slice to the skull in a few seconds if pressure is applied. To avoid this, we let the Portasol rest on the skin for about 10 seconds, causing a shallower burn than if we applied pressure. We expect that changes in these approaches would influence healing, but haven't studied this yet.

Future research

Producers can put their own irons in the fire, so to speak, to explore strategies to reduce healing time. There is still a lot of research to be done. For example, other ways to disbud, like caustic paste and clove oil, have not received much attention. For each disbudding method, there are many unknowns. How long does it take for the wounds to heal? How much pain does the calf have, and for how long? Does it cause scurs? The only pain-free solution is to avoid the procedure altogether by using polled genetics. However, until we have more polled bulls, we will continue to find ways to make disbudding less painful.  

Cassandra Tucker is a professor and director of the University of California - Davis Center for Animal Welfare. Email Cassandra Tucker.

Sarah Adcock - Graduate Student

University of California - Davis

Email Sarah Adcock

Best practice for controlling pain during disbudding

We currently do not have drugs to manage pain over several weeks. However, we can control pain during and in the hours after disbudding using a combination of local anesthetic and NSAID.

When: If paste is used, it should be applied within several days of birth. If a hot iron is used, calves should be disbudded when they are less than 8 weeks old, before the horn buds have attached to the skull. There is no scientific information to suggest that hot-iron disbudding newborn calves is better for welfare, only that this method should be used before the horns really begin to grow. Calves experience pain no matter how young they are, and pain control is needed at all ages and with all methods.

How: Ten minutes before disbudding, give a cornual nerve block with buffered lidocaine on each side of the calf's head. You will need:

• 10 milliliters of 2 percent lidocaine hydrochloride (5 milliliters per horn bud)
• 1 milliliter of sodium bicarbonate (0.5 milliliter per horn bud)
• Two 20-gauge, 1-inch needles
• 12-milliliter syringe, for drawing up lidocaine
• 3-milliliter syringe for drawing up sodium bicarbonate

Add the sodium bicarbonate to the syringe with the drawn-up lidocaine. This will buffer the lidocaine, reducing the sting of injection. Slide the needle completely into the groove behind the corner of the eye at a 45-degree angle to the skin. Slowly inject the solution while redirecting the needle several times to increase the chance of anesthetizing the nerve. Consult with your veterinarian about placement of the needle, as this must be done correctly in order for the block to work. We also use a new needle to administer the block because going through the rubber of the bottle blunts it and removes the coating that helps it slide into the skin. While waiting for the lidocaine to take effect, give the calf an NSAID to help with the longer-term pain - for example, 1 milligram per kilogram oral meloxicam tablets.

After 10 minutes, prick the skin around the horn bud with a needle to ensure the area is numb before applying the iron. If the calf responds, give an additional 2 milliliters of lidocaine at the cornual nerve. When the horn buds are numb, apply the paste or iron.