Disbudding dairy calves with caustic paste: Assessing the effect of contact duration on the healing process

Caustic paste disbudding has grown in popularity in North America. The methods of paste application vary across the literature and affect wound healing. Our objective was to determine whether the duration of paste contact with the horn bud affected paste disturbance by the calf, wound size, healing, and horn regrowth. At 3 d of age, 30 Holstein calves were randomly assigned to 1 of 2 treatments (n = 15 each). Calves were disbudded with a "normal" method, where 0.2 mL of Dr. Naylor's paste was applied to horn buds shaved with a #40 blade and left to dry, or "wiped" where the paste was removed after 1 h. The prevalence of paste disturbance from the calf rubbing a horn bud was observed 1 h and 4 h (normal calves only) after application. Wound diameter was measured 1 d after disbudding and 5 wk later. We evaluated the presence and absence of 8 tissue types and horn regrowth 1-2x/wk for 21 wk. Paste disturbance showed no evidence of differing by treatment (17% vs 23% of horn buds for normal and wiped, respectively, 1 h after application). Disturbance from rubbing did not affect wound size or healing time. Wound diameter was similar between application methods: wounds were (mean ± SE) 18.9 ± 0.5 and 20.1 ± 0.8 mm 1 d after disbudding and 5 wk later increased to 22.7 ± 0.6 and 23.0 ± 0.8 mm for normal and wiped treatments, respectively. There was no evidence that treatment affected the probability of reaching the 3 tissue types evaluated as stages of healing (63 vs. 73% crust, 47 vs. 57% epithelium, and 40 vs. 33% fully healed for normal vs. wiped). Calves with wiped horn buds tended to have more horn regrowth, including regrowth that required removal by a secondary procedure, compared with the normal treatment. Across both treatments, wounds took longer to heal in this study than in previous work: only 37% had fully healed by 21 wk compared with 74% of wounds created by a similar amount of paste in another study. In conclusion, wiping paste after 1 h did not appear to reduce wound size or disturbance from rubbing, or hasten healing, and tended to increase the risk of regrowth compared with letting it absorb.