Experimentally induced disease Histopathological findings in a pilot study of dairy calves disbudded with hot cauterization or caustic paste

Our aim was to describe the histological tissue damage and compare the healing process in 16 dairy calves disbudded at a mean age of 6 days with cauterization (CAUT) or alkaline caustic paste (CAUSTIC). Biopsies were taken 2 days (T2) and 2 weeks (T14) after disbudding from sedated calves treated with local anaesthetics and non-steroidal anti-inflammatory drugs. At T2, the CAUT samples generally had eosinophilic coagulative necrosis of the epidermis and superficial dermis, bordered basally by a neutrophilic demarcation zone. Lateral to the direct heat contact area, dermal blood vessels were thrombosed, with wall damage and perivascular neutrophils. In the CAUSTIC group, the epidermis and dermis had diffuse full-thickness liquefactive necrosis directly under the paste contact area. The necrosis spread laterally in the dermis beyond the area of paste contact and was bordered by a neutrophilic infiltrate. At T14, the CAUT samples had epidermal to superficial dermal ulceration and crusting, dermal neutrophilic infiltration and granulation tissue formation. In contrast, most of the CAUSTIC samples consisted of a superficial dermal crust or predominantly necrotic tissue fragments. The remaining viable areas had histiocytic inflammation with peripheral neutrophils and early granulation tissue formation. Caustic paste disbudding caused poorly demarcated lesions that were more severe and extensive and took longer to heal than those due to cautery. Cauterization induced a more intense acute reaction adjacent to the primary lesion compared with caustic paste.