May 29, 2013
A variety of methods have been used to dock tails in dairy cattle, including cauterizing docking irons, application of elastrator bands, use of emasculators, and surgical excision. The application of elastrator bands is the most commonly employed method. Tail docking in the dairy industry is usually performed on preparturient heifers or calves near weaning age. An elastrator band or tight rubber ring is applied to the tail so that between 1/3 and 2/3 of the tail are removed; in New Zealand, regulations determine the minimum length between the distal vulva and the site of band application.1 Placement distal to the sixth coccygeal vertebra has been recommended to ease the docking process and to avoid leaving a tail that is too short for proper restraint or that parts the vulvar lips and allows manure contamination of the urogenital tract.2 The necrotic distal portion of the tail detaches 3 to 7 weeks after banding, or may be removed by using clean shears. Tail docking in the beef industry at the feedlot requires that the distal 2/3 of the tail be removed immediately after placement of the elastrator band or rubber ring.
Tail tip necrosis can lead to tail infection, ascending myelitis, septicemia, and lameness in cattle that have suffered a tail injury however the risk of subsequent infection from tail injury is low. A study on the prevalence of tail tip necrosis in Ontario Canada found 34.5% of tails inspected at slaughter plants to have necrosis with only 3.4% having infections.13 Another study conducted in Ontario found that cattle housed in solid floor facilities had no tail tip necrosis, whereas 1.36% of cattle housed in slatted floor facilities were treated or slaughtered for tail tip necrosis.11 A similar study in Nebraska found 1% of cattle housed in a slatted floor facility to have tail tip necrosis.14 Tail tip lesions occur most often in cattle without docked tails housed on slats, followed by cattle with docked tails housed on slats.12 The lowest prevalence of tail tip lesions is in cattle housed in solid bedded facilities.11 Severe tail tip lesions occur the most in cattle that are not tail docked and are housed on slatted floors.11 Severe lesions also occur in docked cattle housed on slats however no severe lesions were found on cattle housed in solid bedded facilities.11 Finally, a study identified no differences in performance or health indices between cattle with docked tails and cattle without docked tails housed on slats even though the cattle without docked tails had more tail tip lesions.15
When compared with 7- to 21-day-old calves, banded 22- to 42-day-old calves exhibited significantly more rear visualization and restlessness than intact calves of the same age.19 That study's investigators concluded that, although age-related behavioral differences were observed, tail docking of calves produced a minor response.
Based on measurement of plasma cortisol concentrations of calves before and after tail docking with a rubber ring or cautery iron, Petrie et al20 determined that docking did not result in significantly more distress than restraint and blood sampling. A small number of 3- to 4-month-old calves exhibited tail shaking and vocalization, which was interpreted as discomfort. The use of local anesthetic at the time of ring application provided no detectable benefit in reducing physiologic signs of stress.
Tail docking of adult heifers using an elastrator band with or without local anesthesia resulted in few physiologic or behavioral effects. Banded heifers spent more time eating during the week following banding, which may have represented displacement behavior and mild distress; these behaviors returned to pre-banding levels when necrotic tails were removed. Increases in plasma cortisol concentrations, considered indicators of stress, were not observed.21 Restlessness was observed during the first hour after banding in preparturient heifers, but the finding was not statistically significant.10
Docked heifers spent significantly less time holding their tails in the raised position following docking and significantly more time with their tails in the pressed position, but no differences were observed in feed intake or milk production. Holding the tail in the pressed position was interpreted as an indicator of discomfort. Significantly less tail shaking was observed in docked heifers, and was hypothesized to be related to pain associated with shaking the recently banded tail. No differences were observed in behavior of heifers docked with or without epidural anesthesia. The investigators involved in that study concluded that tail docking was associated with minimal discomfort in heifers, and that use of epidural anesthesia provided no benefit.22
Chronic pain—Following trauma to peripheral nerves (including that induced by banding and docking), continued growth of damaged nerve axons may result in the formation of a mass of tangled axons called a neuroma.23 Neuromas are associated with chronic pain, and may play a role in post-amputation pain in humans.2 Neuromas have been reported to develop after beak trimming in poultry and tail docking in pigs,24,25 and were observed at slaughter in tail stumps of adult cattle that had been docked using a knife at 12 to 18 months of age.26 Eicher et al27 documented increased sensitivity to heat or cold in previously docked heifers. These findings were comparable to those observed in humans experiencing phantom limb pain following amputation, and were interpreted as indicators of chronic pain. In addition, neuromas were identified in the tail stumps of the docked heifers included in the study.
Physiologic stress—Blood cortisol concentrations have been studied as indicators of physiologic stress in animals. Tail docking of preparturient Holstein heifers did not result in significant alterations in cortisol concentrations.8,14,16 Docking of three-week-old calves did not significantly increase blood cortisol concentrations above those associated with handling and sample collection.20
Disease—Necrotic tissue, such as the ischemic distal tail after banding, is prone to infection with pathogens. Clostridial organisms, ubiquitous in soil, may colonize the wound and result in local or systemic infection. Tetanus and gangrene have been reported after tail docking, and vaccination against clostridia is recommended prior to performing the procedure.2
Behavior—The role of the tail in communication between cattle has not been documented, but it has been speculated that tail docking limits the ability of cattle to exhibit normal signaling behavior.28,29 In addition, the tail is widely believed to play a role in fly control; shaking the tail and brushing the body and limbs can dislodge biting flies. Fly avoidance behaviors following tail docking have received attention from researchers for their implications for animal welfare. The stable fly (Stomoxys calcitrans) is a common disruptive fly, and its presence has been associated with increased stress, reduced milk production and weight gain, disrupted grazing, and reduced growth.30 Observed fly avoidance behaviors include stomping, kicking the trunk, tail swishing, skin twitching (panniculus reflex), head and ear motion, and taking flight.8,18
Fly counts have been observed to be greater on the rear limbs of docked three-week-old calves during times of high fly activity.18 Several studies have confirmed that although front limb fly avoidance behaviors did not differ, rear limb fly avoidance behaviors were significantly increased in docked cows when compared with intact cows. 8,31,32,33 In addition, almost twice as many flies were observed on the rear limbs of docked cows compared with control cows.7