Effects of variation in caustic paste application on wound characteristics and healing in dairy calves

Wounds caused by caustic paste take longer to heal than wounds from hot-iron disbudding, but little work has focused on factors influencing healing following caustic paste disbudding. The objective of this study was to evaluate the effects of paste area and thickness on disbudding wound characteristics and healing. Twenty female Holstein calves were randomly assigned to one of 2 paste areas: large (22 mm diameter; n = 10 calves) or small (12 mm diameter; n = 10 calves). Within each calf, one horn bud was treated with a 1-mm thick paste and the other with a 2-mm thick layer (n = 20 buds per thickness level; n = 10 buds per area × thickness combination). Disbudding was performed at 4 to 6 d of age using multimodal pain management (sedation, local nerve block, and analgesics). The healing progress was monitored weekly until wounds had fully contracted. Measurements included wound size and depth, wound tissue type classification, and pressure pain threshold (PPT). The larger paste area created larger wounds than the smaller area (short axis: 23.9 ± 0.64 mm vs. 14.9 ± 0.61 mm; long axis: 25.9 ± 0.67 mm vs. 16.7 ± 0.63 mm). A thicker paste application created larger wounds than a thinner application (short axis: 20.0 ± 0.51 mm vs. 18.6 ± 0.51 mm; long axis: 22.4 ± 0.51 mm vs. 20.3 ± 0.51 mm). The effect of paste area was observed throughout the healing process, but the effect of thickness was observed only while necrotic tissue was present. We detected no effect of treatment on PPT. Evidence of residual horn tissue was observed following disbudding with the smaller paste area, but not when a larger area was applied. In conclusion, creating smaller wounds promotes faster healing following caustic paste disbudding, but may increase the risk of scur development.