| Summary: | ABSTRACT: Disbudding is a common painful procedure. Farms vary in method (e.g., cautery or paste), whether the horn bud hair is shaved, or in the quantity of paste applied, for example. However, little research compares the long-term effects among these methods. Our objective was to describe wound healing, sensitivity, and horn regrowth following cautery and 2 methods of caustic paste disbudding. Female Holstein calves were assigned to 1 of 4 treatments (n = 25/treatment): non-disbudded sham (Control), 12.7-mm hot iron leaving the bud in (Hot Iron), 0.2 mL of paste on shaved horn buds (0.2 Shaved), or 0.3 mL of paste on unshaved horn buds (0.3 Unshaved). Before disbudding, at 3 d of age, calves received a local block and systemic pain relief. Wounds were scored 1 to 2×/wk until they were fully healed and only a thin scar line remained. Nine tissue types were scored, including epithelium, when the wounds were covered in a new layer of skin. Wound depth, diameter, and mechanical nociceptive threshold (MNT) measures to evaluate sensitivity were collected 4, 14, 28, and 42 d after disbudding. Compared with Controls, all disbudded calves exhibited lower MNT values in the first 42 d, whereas sensitivity was similar among disbudding treatments. Wound diameter was similar 4 d after disbudding. In the following weeks, wounds from Hot Iron contracted, whereas those from paste first increased in size. Wound depth in the weeks after disbudding was smaller for Hot Iron than caustic paste. Paste wounds took 16 wk to re-epithelialize and 17 to 18 wk to heal, and this was at least twice as long as cautery disbudding, where these stages were reached after 7 and 10 wk, respectively, on average. Horn regrowth was present in 4% of buds from both Hot Iron and 0.3 Unshaved, and 8% from 0.2 Shaved. Applying 0.2 Shaved or 0.3 Unshaved treatments created similar wound size, sensitivity, healing, and regrowth, confirming the likeness of these ways of chemically destroying horn growing tissue. Taken together, all wounds were more sensitive than un-damaged tissue for at least 42 d, and paste wounds were deeper and increased in size, whereas Hot-Iron wounds contracted. Paste wounds also took at least twice as long to re-epithelize and fully heal compared with those from cautery disbudding. These results highlight the importance of understanding methodological differences associated with routine management procedures and, when viewed in combination with other available information, suggest cautery disbudding is better for calf welfare than caustic paste.
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