Dehorning dilemmas

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click image to zoom It’s been shown that disbudding young calves before they reach three weeks of age is the least stressful and painful time to do this practice as the horn buds are not yet attached to the skull. After the horn buds attach to the skull, at around 2 months of age, dehorning to remove them is required.

While various methods of disbudding (caustic paste, hot-iron, etc.) and dehorning (wires, shears, knives, etc.) are available, all of them usually involve some discomfort or pain during and after the procedure. In 2008 the American Veterinary Medical Association (AVMA) released a position statement that “Because castration and dehorning cause pain and discomfort, the AVMA recommends the use of procedures and practices that reduce or eliminate these effects, including the use of approved or AMDUCA-permissible clinically effective medications whenever possible.”

In early 2011, AVMA released a video promoting its policy on disbudding/dehorning and using analgesics (visit www.AVMA.org). In it, it encourages using lidocaine and non-steroidal anti-inflammatory drugs (NSAID) for post-operative pain.

It’s important to get a snapshot of current pain mitigation practices by producers and veterinarians who disbud/dehorn calves. Hans Coetzee, BVSc, Cert CHP, PhD, Dipl. ACVCP, Kansas State University, says a survey of north central and north eastern United States dairy producers showed that only 12.4% of dairy producers use local anesthetic nerve blocks and only 1.8% provide systemic analgesia at the time of dehorning (Fulwider et al., 2008). Similarly, only 18% of Wisconsin dairy producers report using local anesthetics prior to dehorning (Hoe et al., 2006). “These data are consistent with the results of the recent 2009 National Animal Health Monitoring System (NAHMS) survey that reported that only 17.7% of U.S operations report using analgesics or anesthetics during the dehorning procedure,” Coetzee says.

Suzanne Millman, PhD, Iowa State University, says a group at the Ontario Veterinary College surveyed dairy producers and dairy veterinarians about pain associated with dehorning. “We were surprised to find that 92% of bovine veterinarians and 22% of dairy producers use a local anesthetic for dehorning some or all calves,” she says. “Both veterinarians and producers cited pain relief as primary reason, whereas time and cost were cited as reasons for not using analgesia. The significant take-home message for bovine practitioners from this study was that producers who used analgesia were 6.5 times more likely to have a veterinarian involved with their decision-making about dehorning, whereas 13% of producers were unaware of opportunities for pain management.”

Millman believes the attitudes about pain management by food animal practitioners in other countries reflect the clarity of expectations. “In countries where pain management is regulated, practitioners are placing their focus on identifying the most effective products that are economical and that are easily administered, rather than the debate about whether pain management is necessary,” she explains.

click image to zoom Millman says anesthesia is being phased in for piglet castration in the European Union and has been a requirement in several countries for a few years now. “There is also a move to eliminate the need for these procedures in some countries, such as Norway, by marketing boars and bulls at younger ages and by changing husbandry practices to control aggression in intact males and horned cattle,” she adds. “However, these options are not easily transferred to the U.S. production system due to differences in economic incentives and the scale of production/herd size, but may be options for some of the niche producers.”

Millman recently met with some swine veterinarians from Switzerland who explained their regulations for anesthesia and analgesia for piglet castration. There, anesthesia and postsurgical pain management are required by law, and the standard practice is injection of an NSAID prior to the procedure followed by isofluorene anesthesia. “The veterinarian’s responsibility is to prescribe the medications and certify the training of the producers who will perform the procedures. These veterinarians strongly supported the use of pain management medication, and their focus was on their ability to validate the producers were following the standard operating procedures.” The equipment used for this purpose tracks the number of piglets processed and the drug inventory.

Millman uses this example to show the enormous variation in how countries are attending to animal welfare issues and what the veterinarian’s role is. “It is hard to imagine how some of these policies could be implemented in the U.S., due to the importance of our export markets, but we also need to be aware of the general shift in international attitudes about pain.”

In all species, including humans, pain can only be measured indirectly, so interdisciplinary scientific approaches are needed. Millman adds that pain assessment can be quantified using physiologic changes, neuroendocrine markers, subtle behavior changes and pain withdrawal response tests, but these techniques do not easily lend themselves to field trials due to technical expertise needed and costs. In Europe, Canada, Australia and other countries, approval has been achieved using laboratory rather than field data.

Pain in the young calf

Pain associated with dehorning is significant and there is no evidence that less pain is perceived when we perform surgeries at younger ages in precocial species (those which are born ambulatory and relatively independent versus those such as humans that are dependent for a period of time), Millman explains.

Pain assessment requires an interdisciplinary approach. “Pressure algometry is considered just one measure, but it perhaps gives us the closest approximation of ‘asking’ the calf what she feels,” Millman says. Pressure algometers measure the amount of force that is exerted on a surface and it is fast, inexpensive and easy to use. “In our experiments, we apply pressure to four landmarks or locations around each horn bud and remove the device when the animal exhibits a withdrawal response.”

In the calf dehorning studies, the calf is restrained using a halter, the algometer is applied perpendicularly to the calf’s head at a steady rate of approximately 1kg force per second, and as soon as the calf moves its head away from the device, the force is recorded. “We were the first to use pressure algometry to measure bovine pain in experiments in 2004-2005, and this was published in Journal of Dairy Science,” Millman says. “At ISU, we have been developing the technique further to see if it would be a candidate for field trials.”

In 2009 Iowa State University veterinary student Kristyn van Donselaar conducted a research project refining the calf restraint using a head restraint device. The calf was blindfolded so the technician would be less likely to influence the calf response and differences between technicians were examined by having one person measure pain on one horn bud and the second person measuring pain on the other horn bud on the same calf. The response when the pressure algometer was applied to the painful sites around the horn bud relative to a non-painful site (the face) were also compared to differentiate between the calf simply wishing to be left alone versus being in pain.

“The results are very promising and this appears to be a robust measurement tool not only for measuring pain reliably in the calf in the laboratory, but for taking it out to the field where multiple researchers are involved,” Millman says. “We are in the process of writing this research up for publication, and we are further applying the algometer techniques in our experiments with dairy lameness, sow lameness and other painful conditions.”

There are advantages to performing dehorning early in regard to attachment of the horn buds to the skull and simply the size or extent of the damage inflicted when the horn buds are small. “One of the more subtle benefits for the beef calf is the supporting influence of the dam,” Millman says. “The dam is very attentive to pain and illness in the calf and can aid convalescence by encouraging feeding, facilitating rest and protecting the calf from bullying or social stressors.”

The calf that is castrated and dehorned at weaning is subjected to multiple stressors and is not primed for healing and convalescence. In addition to the novel pathogens the calf is exposed to and the social mixing with unfamiliar animals, the calf may not have had opportunity to explore its environment to identify food, water and resting resources. “Animals experiencing pain withdraw from their social companions, spend more time resting and are less interested in exploring, and for these reasons these calves will be particularly unlikely to flourish and transition to the feedlot environment,” Millman adds. “Similarly, cow-calf producers should consider providing calves with opportunity to explore the environment in which they will be housed after processing before beginning these procedures, although if the calf is still with the cow the cow can guide him.”

Available products and their challenges

Products that can be administered at the time of dehorning include local anesthetics such as lidocaine and bupivicaine. Coetzee says these are effective against immediate incisional pain (acute pain) but have little or no effect against chronic pain associated with inflammation. “Studies show that a well-placed cornual nerve block that is allowed sufficient time to take effect can reduce and sometime eliminate an acute (<1 hour) increase in serum cortisol after dehorning,” he explains. However this effect only lasts for the duration of local anesthesia (4–6 hours) after which a “rebound” increase in serum cortisol is typically observed.

There are challenges associated with the routine use of local anesthesia. “Accurate placement of the cornual block requires training,” Coetzee says. “Complications include inadvertent intravenous injection or incorrect placement of the block with respect to the anatomical location of the nerve.” Producers should be trained by a veterinarian to perform a cornual nerve block.

The injection site is the upper third of the temporal ridge, about 2.5 cm below the base of the horn. The nerve is relatively superficial, about 0.7–1 cm deep. Typically the block involves administration of 3–5 ml of 2% lidocaine injection.

Normally there is a 5–10 minute delay between administration and the onset of activity depending on the volume of local anesthetic administered and how well the block was placed relative to the location of the nerve. “This is feasible to do in dairy operations when the calves are in hutches but may be challenging in beef cattle since this may significantly slow processing,” Coetzee notes.

The duration of a local anesthetic is about 3–6 hours. This can be overcome with “multimodal analgesia” — using a combination of analgesics that have activity at multiple locations along the pain pathway. Coetzee says combining local anesthesia and a non-steroidal anti-inflammatory drug (NSAID) would be an example.

NSAIDS, sedatives and the DEA

Non-steroidal anti-inflammatory drugs include meloxicam (see sidebar), ketoprofen, aspirin and flunixin. “These products are not effective against immediate incisional pain, but are effective against chronic pain associated with inflammation,” Coetzee explains.

Veterinary student Anneliese Heinrich’s studies at the Ontario Veterinary College found significant differences in pain responses up to 24 hours after dehorning for calves that received meloxicam versus those that did not. “More recently, our group at Iowa State University found significant pain responses using the algometer test for 59 hours after disbudding (calf age 14–21 days) versus calves that were sham disbudded with a cold dehorning iron,” Millman says. “Lidocaine was administered to all calves and this mitigated disbudding pain for approxi-mately one hour. “Sedative analgesics include xylazine, ketamine and butorphanol. Coetzee notes that these drugs are Schedule 3 and therefore require a U.S. Drug Enforcement Administration (DEA) license and are subject to regulation by the DEA. Therefore, application of these compounds to provide pre-emptive analgesia is restricted to use by licensed veterinarians. “They are effective at mitigating an acute cortisol response but are ineffective against pain caused by inflammation,” he adds.

Economics

“The cost associated with providing preemptive analgesia contributes to the reluctance of producers to adopt these measures especially since there is no perceived economic benefit for doing so,” Coetzee adds. “It may also be difficult for producers and veterinarians to determine if analgesic compounds are effective because cattle may not show overt signs of pain and distress. Thus determining the need for analgesia and the dose, route, duration and frequency of drug administration in cattle can be especially challenging.”

But these are things the industry needs to start considering. “California has already placed restrictions on bovine tail docking so I think it is important for bovine practitioners to have this on their radar,” Millman states. “Efforts to use polled genetics and to ensure that best management practices are followed are immediate steps we can apply. Similarly, thinking through how to improve welfare by aiding convalescence in the absence of analgesia is a concept worth consideration and communicating with the public.

“Producers and practitioners can pause and think through the healing process and tailor these considerations for their particular situation,” Millman adds. “No one wants to see an animal in pain or ill. Ensuring the animal has protection from extreme weather, bullying, that it has a warm, dry comfortable place to rest and that high quality food and water are available are important. Factors such as these will set the animal up for swift and successful recovery.” 

For information on using anesthesia and a diagram of the bovine head for cornual blocks, see “Local Anesthetic Techniques” by Ron Mandsager, DVM, Dipl. ACVA, here.

Sidebar: What we know about meloxicam

The pharmacokinetics of meloxicam after oral and IV administration have recently been described by researchers at Kansas State University. Hans Coetzee, BVSc, Cert CHP, PhD, Dipl. ACVCP, says a mean peak plasma concentration (Cmax) of 3.10 ug/mL (range: 2.64–3.79 ug/mL) was recorded at 11.64 hours (Range: 10–12 hours) with a half-life (T ½ lz) of 27.54 hours (range: 19.97–43.29 hours) after oral meloxicam administration. The average bioavailability (F) of oral meloxicam corrected for dose was 100%. “These findings indicate that oral meloxicam administration could be an effective and convenient means of providing long-lasting analgesia to ruminant calves at dehorning,” Coetzee says.

The use of lidocaine in combination with meloxicam is a viable option for short and longer-term pain relief. Administration of lidocaine alone only mitigates the acute pain response, and will only last up to 3–4 hours. “Administration of meloxicam only does not mitigate the response to acute pain but will reduce pain and inflammation for a period after dehorning,” Coetzee says. “The best approach is to combine these drugs using multimodal analgesia. This effect will likely last several days based on the pharmacokinetics of the drug.”

Meloxicam (20 mg/ml) is approved for use in cattle in several European countries with a 15-day meat withdrawal time and a 5-day milk withdrawal time following administration of 0.5 mg/kg IV or SC. A meat withdrawal period of 20 days has been
established in Canada after SC administration of meloxicam at 0.5 mg/kg.

In the United States, the injectable form is only available in dogs and its use is cost-prohibitive in food animals. Coetzee says human generic meloxicam tablets could potentially be provided in the milk replacer. This indication constitutes extra-label drug use (ELDU) which can only be conducted under the supervision of a veterinarian and provided a valid veterinary-client-patient relationship is in place.

“Based on the pharmacokinetics of meloxicam a maximum plasma concentration is achieved 12 hours after oral administration,” Coetzee says. “Therefore the optimal timing of meloxicam administration is 12 hours prior to disbudding or conveniently, the night before the procedure.” He adds that a study comparing the pharmacokinetics of oral meloxicam in pre-ruminant and ruminant calves has recently been concluded at Kansas State University. “Preliminary results suggest that the plasma concentrations in the two classes of animal are comparable.” Lidocaine takes 5-10 minutes before the maximal effect is observed.

The cost of human generic meloxicam tablets is around $0.25/100 lbs. bodyweight, and 100 ml of lidocaine costs around $3.95. “Assuming a dose of 10 ml/ head that assumes a cost per animal of $0.39,” Coetzee says.

Sidebar: Canada’s guidelines on dehorning/disbudding

Canada recently approved meloxicam for use in longer-term pain control of calves being disbudded/dehorned. New Canadian guidelines recommend disbudding at less than 3 weeks of age.

Research by Anneliese Heinrich, a Master’s student of Suzanne Millman, PhD and Todd Duffield, DVM, DVSc, Ontario Veterinary College, Guelph, was used to support a Canadian label claim for meloxicam in bovines for mitigation of pain associated with dehorning. “By using cortisol, heart rate, respiratory rate, activity, video analysis of behaviors in the home pen and the algometer pain test response, her research found evidence that this non-steroidal anti-inflammatory drug decreased pain-related stress and behaviors,” Millman explains.

An excerpt from Canada’s national Farm Animal care Council Code of Practice for Dairy Cattle under the disbudding/dehorning section, says: “Pain control reduces animal discomfort during disbudding and dehorning. Local anesthetics can reduce the pain caused by the procedure, but do not provide adequate post-operative pain relief. The most popular local anesthetic, lidocaine, is effective for two to three hours after administration. The use of analgesics in addition to a local anesthetic can minimize pain and stress in the hours that follow dehorning. The use of a sedative can essentially eliminate calf response to the administration of the local anesthetic and the need for physical restraint during the administration of the local anesthetic and during disbudding/dehorning. Thus a combination of sedative, local anesthetic and an anti-inflammatory reduces the response to pain during and after disbudding/dehorning. The above drugs are only available with a valid VCPR.



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Nathan Cline    
Iowa  |  June, 13, 2011 at 06:17 PM

THe easiest, least painful method of dehorning is breeding for natually polled cattle. All 6 major US breeds have some purebred polled animals, as well as the Swedish and Norwegian Red breeds used for crossbreeding. Because the polled gene is a simple dominant, it can be quickly inserted into any cow herd through use of polled herd sires or frozen semen. A heterozygous polled bull will produce approx. 50% polled calves.


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