April 20, 2012
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Disbudding and dehorning of cattle in the United States is not currently regulated. The Canadian Veterinary Medical Association recommends that disbudding be performed within the first week of life.10 In the United Kingdom, disbudding with a hot iron is preferred to dehorning and it is advised that this should be performed before cattle reach the age of 2 months.11 Application of caustic paste is acceptable in cattle up to 7 days old,12 but anesthesia is required if cattle are dehorned after this period.12,13 Australian and New Zealand authorities recommend disbudding at the youngest age possible, and chemical dehorning is not deemed to be acceptable unless it is performed within the first few days after birth.14-17 In Australia, dehorning without local anesthesia or analgesia is restricted to animals less than 6 months old.2,12 The New Zealand Code of Welfare for Painful Husbandry Procedures mandates a 9 month age limit for dehorning without attention to pain relief17 The 1992 Animal Rights Law in Sweden requires that dehorning via cautery be performed under anesthesia/sedation.6,12 In Denmark, calves up to 4 weeks old can be dehorned without application of a local anesthetic.12
A survey of dairy farms in in the northeastern provinces of Italy regarding dehorning methods has shown the practice of dehorning is carried out in 80% of the dairies surveyed.18 In the surveyed group, hot-iron disbudding was the method most commonly used (~91%) with the remaining dairies using caustic paste.18 Of the farmers surveyed, 10% utilized local anesthetics as part of their dehorning protocol and only 5% administered an analgesic.18 When questioned about post-procedure pain nearly half of the farmers perceived that pain in calves lasted more than a few minutes.18
Dehorning cattle conveys advantages. Horns are the single major cause of carcass wastage due to bruising,16 and trim associated with bruising for carcasses from horned cattle is approximately twice that for carcasses from hornless cattle.12 Dehorned cattle require less feeding trough space; are easier and less dangerous to handle and transport; present a lower risk of interference from dominant animals at feeding time; pose a reduced risk of injury to udders, flanks, and eyes of other cattle; present a lower injury risk for handlers, horses, and dogs; exhibit fewer aggressive behaviors associated with individual dominance; and may incur fewer financial penalties on sale.1,2,8,13,17,19-21
Physiologic and behavioral indicators have been used to assess acute distress responses to potentially painful husbandry procedures. Tissue damage (e.g., from disbudding and dehorning) results in activation and release of intracellular contents from damaged cells, inflammatory cells, and nerve fibers.22 Physiologic, neuroendocrine, and behavioral changes indicative of pain and distress are observed following dehorning.5,23
Physiologic indicators—Although responses vary slightly according to dehorning method, plasma cortisol concentrations increase rapidly 30 to 60 minutes after dehorning, decline slightly, plateau level for 3 to 4 hours, and then return to baseline values approximately 6 to 8 hours after the procedure.24-30 Assessment of the catecholamine (fight or flight) response allows evaluation of the acute responses to painful procedures, but this response is short-lived and relevant only to the earliest phases of the distress response.26 Adrenaline (epinephrine) concentration was increased 5 minutes after scoop dehorning of 10-week-old calves; was not affected by use of local anesthesia, and returned to baseline within 10 minutes.26 Noradrenaline (norepinephrine) concentrations may also rise due to tissue release of noradrenaline in response to injury; increased noradrenaline concentrations were observed 10 minutes after dehorning, but had returned to baseline levels within 60 minutes.26 Eye temperature drops either during dehorning or after local anesthesia wore off due to sympathetic activity leading to vasoconstriction and redirection of the blood.27,28
Although dehorning using a scoop resulted in slightly higher cortisol concentrations than dehorning via saw, guillotine shear, or embryotomy wire, there was little difference in distress displayed by 5- to 6-month-old calves in response to these methods.27 Decreasing the depth to which the scoop was applied during dehorning did not reduce the magnitude of the plasma cortisol response in 14- to16-week-old calves.24 On this basis, the investigators concluded this approach was not effective in reducing associated pain and distress. Another study has shown that cortisol concentrations in the blood were higher in scoop-disbudded calves than in hot-iron or caustic paste disbudded calves up to 6 hours post-disbudding.31 This study also noted that cortisol concentrations in the blood were significantly higher in caustic paste disbudded calves than hot-iron disbudded (without anesthetic) calves at 1 hour post-disbudding, possibly indicating more intense pain at that time point.31 It is important to note that the ages of these groups of calves differ as the various techniques have different age windows for utilization.
Behavioral Indicators—Avoidance behaviors observed during dehorning include tail wagging, head movement, tripping, and rearing.13 Postoperative indicators of pain include head rubbing, head shaking, neck extension, ear flicking, tail flicking, increased numbers of transitions between lying and rising and reduced rumination.13,31,32 One study has shown that hot-iron disbudded calves that have not been given any anesthetic show more struggling during disbudding and more postoperative indicators of pain after disbudding than scoop and caustic paste disbudded calves.31 Scoop disbudding is thought to be equally painful during the procedure however it is very quick so the animal does not have to struggle to get away from the source of pain.31 Scoop disbudding is comparable to caustic paste and hot-iron disbudding (without anesthetic) with regards to postoperative indicators of pain at 1 and 3 hours post-disbudding.31 Post-disbudding caustic paste has been shown to produce more transitions between lying and rising than hot-iron disbudded (without anesthetic) calves.31 At 6 hours post-disbudding scoop disbudded calves show more postoperative pain behaviors than either caustic paste or hot-iron (without anesthetic) disbudded calves.31 The use of high tension elastic rubber bands has been shown to cause significant changes in attitude, gait and posture, and increased time spent lying down when compared to mechanically dehorned or tipped cattle.33 Banded cattle also have decreased appetites and poorer wound healing following the dehorning procedure than cattle that have been mechanically dehorned or tipped.33
Disease—Tetanus has been reported as affecting cattle after dehorning,34 and prophylaxis is recommended. Bovine cutaneous papillomas have also developed after dehorning of 3- to 4-month-old calves due to physical transmission of virus particles via equipment.35
Physical dehorning has been associated with an increased risk of transmission of the bovine leukosis virus (BLV). Lassauzet et al36 observed that risk of BLV infection increased from 8% to 77% when cattle were gouge dehorned. Gouge dehorning of 6- to 12-month-old heifers resulted in transmission of BLV via physical transfer of infected blood by the dehorning device; after changing to electrical dehorning of cattle at 8 weeks of age, prevalence of BLV in the herd decreased from 67.7% to 40.3% in 3 years.37,38
Production—Although reduced body weight gain was observed during the first 6 weeks after physical dehorning of 4-, 7-, 19-, and 30-month-old calves, final mean body weights of all groups were not significantly different than those of control (naturally polled) calves.39 No significant difference was observed in weight gain between polled animals, previously dehorned cattle, and recently dehorned stocker cattle.21 Feed intake and growth rate were not significantly different in electrically dehorned versus control calves at 8 weeks of age.40
Sedation—Although sedation with xylazine and/or butorphanol reduced the occurrence of avoidance behaviors during disbudding/dehorning, sedation alone was not effective in reducing the cortisol response to hot-iron disbudding.41
Cauterization—Cauterization of the wound following scoop dehorning with a local anesthetic virtually abolished the cortisol response for 24 hours in 3- to 4-month-old calves.42 In addition, blood loss was minimal and no complications were observed during wound healing. Cauterization after scoop dehorning of 5- to 6-month-old calves produced a transient rise in plasma cortisol concentration associated with the pain of the cautery procedure; however, when combined with local anesthesia, the cortisol response was virtually abolished throughout the 9-hour postoperative observation period.41
Local anesthesia—Many sources now recommend that local anesthesia be provided. Anesthesia reduces avoidance behaviors during the disbudding/dehorning procedure.12,20,44 Investigation of the benefits of local anesthesia (in the form of a preoperative cornual nerve block with lidocaine or bupivicaine) has produced conflicting results. Local administration of lidocaine prior to electric dehorning of 7- to10- and 14- to 16-week-old calves did not significantly reduce plasma cortisol levels, suggesting that the anesthetic did not reduce stress associated with dehorning.45 McMeekan et al25 observed that local anesthesia prevented an increase in plasma cortisol concentrations in 3- to 4-month-old calves undergoing dehorning only for the duration of effect of the anesthetic; once the anesthetic wore off, a marked increase in plasma cortisol concentrations was observed. Similar results were observed in 6- to 8-week-old calves,8 10-week-old calves,26 and 3- to 4-month-old calves.32 Local anesthesia virtually abolished behavioral indicators of pain for the duration of its action; after the anesthetic wore off, however, calves displayed behavioral changes similar to those displayed by calves dehorned without local anesthesia.20 Overall cortisol response was not significantly reduced, but a rise in plasma cortisol concentrations was delayed by administration of bupivicaine; preoperative administration of bupivicaine attenuated the increase in cortisol concentrations for 4 hours, but a marked rise in plasma cortisol concentration was observed once the effects of the bupivicaine wore off.35 Administration of bupivicaine locally prior to scoop dehorning, followed by a second dose 4 hours later almost abolished the cortisol response for 8 hours.46 Application of local anesthetic prior to disbudding/dehorning with caustic paste did not attenuate behavioral indicators of distress, possibly because the basic pH of the caustic paste negatively affected the action of the local anesthetic.5 Disbudding using caustic paste in 10- to 35-day-old calves resulted in fewer behavioral changes than disbudding using a hot iron.5 Recently, a preoperative cornual nerve block with 100% ethanol has been shown to provide superior analgesia when compared to a cornual nerve block with 2% lidocaine.47
Analgesia—Administration of nonsteroidal anti-inflammatories (NSAIDs) results in prolonged postoperative analgesia.22 Oral administration of ketoprofen prior to and 7 hours after hot-iron dehorning of 4- to 8-week-old calves significantly reduced head shaking, ear flicking, and head rubbing for at least 24 hours.13 In addition, the investigators observed a tendency toward greater weight gain on the first day after surgery compared with control calves.13 Intramuscular administration of ketoprofen to 3- to 4-month-old calves prior to scoop dehorning slightly reduced the initial plasma cortisol peak, but abolished the plateau phase.25 Intramuscular administration of ketoprofen to calves 2 days to 2 weeks old produced a slight, transient reduction in cortisol concentration after disbudding with a butane dehorner.19 The investigators speculated that ketoprofen may be more effective in older calves and calves disbudded using other devices. Sodium salicylate administered either alone or in conjunction with sedation (intramuscular xylazine, ketamine, butorphanol), also significantly reduced the cortisol response associated with simultaneous castration and dehorning.48 In addition, sodium salicylate reduced the decrease in ADG from simultaneous castration and dehorning.48
The combination of a local anesthetic and ketoprofen administered prior to scoop dehorning of 3-to 4-month-old calves virtually abolished the rise in plasma cortisol concentration routinely observed after dehorning.25 In studies using local anesthesia in conjuction with NSAIDS other than ketoprofen, Meloxicam was found to effectively alleviate pain following dehorning by cauterization,28,49,50 but phenylbutazone31 did not reduce the cortisol response to scoop dehorning.
Availability and use of pharmaceuticals—Although combined use of an anesthetic and analgesic appears to represent the most effective method for controlling pain associated with dehorning, regulatory access and cost remain obstacles to practical application. Ketoprofen is not currently FDA-approved for labeled use in livestock in the United States. The only approved NSAID is flunixin meglumine, which has not been demonstrated to have equivalent analgesic efficacy and is approved only for intravenous delivery for the treatment of respiratory disease, mastitis, or endotoxemia. The use of pharmaceuticals can burden producers in terms of both direct and indirect costs; the latter are associated with time delays and a potential need for more veterinary assistance. Extra-label use of anesthetics and analgesics, while potentially an option, is not ideal. Knowledge of effectiveness is not as great as it is for drugs approved for particular species and purposes. Extra-label use can also discourage research and development necessary to approve drugs for specific purposes.
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