Effects of hot-iron application method on wound characteristics and healing in dairy calves

Hot-iron disbudding is the most commonly used method for horn bud removal in dairy calves. Although factors such as post-treatment care, calf age, and the type of hot iron used have been studied in relation to wound healing, procedural factors, such as application time and tip size, have received little attention. The objective of this study was to evaluate the effects of hot-iron application time and tip size on wound characteristics and healing progression. Female Holstein calves (n = 24) were randomly assigned to 1 of 2 application times: 10 s versus 20 s. Within each calf, one horn bud was disbudded using a small tip and the other with a large tip. Disbudding was performed at 28 d of age using multimodal pain management (sedation, local nerve block, and analgesics). Wound size and depth were measured on the day of disbudding and every 3 d thereafter until the wounds had fully healed. Wounds were also photographed for classification of tissue type. Wounds resulting from the large tip were larger and shallower than those created with the smaller tip, requiring more time to achieve a crust-free state (51.9 ± 2.04 d vs. 45.3 ± 2.04 d). Wounds from the 20-s application were larger and deeper than those from the 10-s application, but this did not result in increased time to a crust-free state. Evidence of residual horn tissue after disbudding was observed in 18 of the 24 buds treated with the small tip versus 6 of the 24 treated with the large tip. These findings suggest that a smaller tip size can reduce wound size and shorten healing times following hot-iron disbudding, but can also increase the risk of horn tissue development; however, application duration appears to have a negligible influence on healing.