The effect of disbudding age on healing and pain sensitivity in dairy calves

Abstract

Hot-iron disbudding, a husbandry procedure performed in dairy calves in which horn bud growth is prevented through tissue cauterization, produces severe burns. Little is known about how long pain persists following disbudding or factors, such as age at the time of disbudding, that may influence animal welfare outcomes. Our objectives were (1) to evaluate whether disbudding age mediates healing, pain sensitivity, and weight gain in calves disbudded near birth (3 d) compared with at a later age (35 d); and (2) to examine how long wounds are sensitive during healing. Forty-eight calves were disbudded or sham-disbudded at 3 or 35 d of age (n = 12/treatment). We assessed pain sensitivity with a pressure algometer on d 3 and 7 after disbudding and then weekly thereafter until the wound had re-epithelialized. Sensitivity was measured at the lateral and caudal edges of each wound, as well as on the rump to test for systemic changes in sensory function. We evaluated healing by scoring the presence of 7 tissue types in the wound bed: attached necrotic tissue, detached necrotic tissue, burns outside the necrotic ring, exudate, granulation, crust, and epithelium. Tissue scores, surface temperature, and girth circumference as an estimate of weight gain were measured twice weekly until the wound had re-epithelialized. Disbudded tissue was more sensitive than nondisbudded tissue for at least 3 wk, after which time the sham calves were removed from the study to be disbudded. Wounds took 62 ± 10 d (mean ± SD) to re-epithelialize and were more painful than new epithelium throughout this time, regardless of whether the procedure occurred at 3 or 35 d of age. The surface temperature of disbudding wounds did not differ from that of non-disbudded tissue nor did disbudding affect weight gain at either age. Age at the time of disbudding did not affect latency to re-epithelialize or wound sensitivity. However, rump sensitivity was greater in calves disbudded at 3 versus 35 d of age on d 28, 42, and 56 after disbudding, in agreement with other studies showing increased pain sensitivity when painful procedures are performed at an early age. In conclusion, wounds remain painful throughout healing, raising animal welfare concerns about hot-iron disbudding. Performing the procedure near birth does not improve welfare outcomes; rather, some evidence suggests it may produce a generalized long-term increase in pain sensitivity.

Conditioned place preference reveals ongoing pain in calves 3 weeks after disbudding

“…Our secondary objective was to confirm findings from previous studies that the wounds are sensitive during healing. We predicted that disbudded calves would be more sensitive to mechanical stimulation of the wounds than sham calves regardless of time since disbudding, consistent with previous findings 4,6 .…”

“…The calf was restrained in the head device and blindfolded. We then applied an increasing amount of force to the edge of the disbudding wound, or intact horn bud for sham calves, as described previously 4 . The test ended when the calf moved her head or a maximum cut-off point of 10 N was reached.…”

“…The resulting burns from disbudding remain sensitive to mechanical stimulation until they have re-epithelialized, which takes from 6 to 13 weeks 4,5 . Others reported increased sensitivity for at least 14 weeks, after re-epithelialization had concluded 6 .…”

“…We chose lidocaine as the analgesic agent because it has a quick onset (1-5 min), short duration of action (90 min), negligible side effects, and established antinociceptive efficacy in calves 12 . The selected timepoints after disbudding, 6 hours and 20 days, represent respectively the acute post-operative period and a period of transition when the initial necrotic tissue begins to peel away from the scalp and eventually falls off, leaving an open wound 4,5 . Since wounds vary in healing time 4,5 , we also documented the tissue types present in the wound bed to verify the healing stage at these timepoints.…”

Clove Oil Delays Rather Than Prevents Scur/Horn Growth in Dairy Cattle

“…A multimodal approach to pain management involving administration of local anaesthesia in conjunction with a non-steroid anti-inflammatory drug can mitigate the pain associated with the initial nociceptive damage caused by the cautery iron and the longer-term inflammatory pain associated with thermal burns and has been demonstrated in calves to reduce or abolish the pain response to disbudding [4][5][6][7]. However, even if pain relief is provided, disbudding still causes tissue damage that can lead to infection and longer-term pain [8,9]. In addition, providing pain relief has economic considerations such as cost of the drugs, veterinarian and extra labour.…”