use of infrared thermography to assess inflammation associated with hot-iron and freeze branding in cattle

Infrared thermography was used to compare differences in extent and duration of inflammation observed on hot-iron and freeze brand sites as an indicator of tissue damage and the associated discomfort to the animals. Thirty beef heifers of mixed breed were assigned to either hot-iron (H) or freeze (F) branding treatments according to a predetermined randomized branding order. Ten animals were branded each day over a 3-d period. On the day prior to branding, animals were clipped to expose two patches of skin; one to be used for the branding treatment and the other for a control. Thermographic images of control and treatment sites were made at 0.08 h (5 min) prior to branding, immediately after the brand was completed (0 h), as well as 0.08, 2, 4, 8, 12, 24, 48, 72, 96, 120, 144 and 168 h after branding. Control site temperatures were subtracted from treatment site temperatures for each individual animal. Both F and H brand sites were consistently warmer (1.9 +/- 0.3 and 1.6 +/- 0.3 degrees C, respectively) than corresponding control sites between 2 and 168 h after branding. Treatment differences were obtained at 0, 0.08, 2, 8, and 144 h after branding (P < 0.001, 0.05, 0.005, 0.001, and 0.01, respectively). Freeze brand sites were warmer at 2 and 8 h after branding while H sites were warmer at 144 h after branding. The thermographic evaluation of hot-iron and freeze brand sites indicated that both methods caused tissue damage. However, H brand sites remained significantly warmer than F sites at 168 h after branding. In addition, H sites were significantly warmer than control sites while F sites were not warmer than control sites at 168 h. The prolonged inflammatory response observed in H animals indicates that more tissue damage and perhaps more discomfort are associated with H branding.