Schoiswohl, J., Stanitznig, A., Smetanig, C. et al. 2022. Comparison of alternative methods for thermal disbudding in calves. Journal of Veterinary Behavior 51, 35-42.

Calves are frequently disbudded to reduce the number of injuries due to horns to other animals and farm workers. The most commonly used method is thermal disbudding which is increasingly causing animal welfare concerns (Stafford and Mellor, 2011; Sutherland et al., 2013, Cozzi et al., 2015). The objective of our study was to evaluate alternative disbudding methods either by injection of clove oil or its synthetic analogue isoeugenol. Forty Simmental calves (26 male, 14 female) aged between 1 and 5 days were treated using 4 different methods (n = 10): injection of 1.5 mL clove oil, injection of 1.5 mL isoeugenol, injection of 1.5 mL isotonic NaCl solution (control group) and thermal disbudding. For thermal disbudding sedation and local anesthesia were legally required. Horn growth of all calves was repeatedly measured. Computer tomography (CT) of the horn bud region and histological examination of biopsy samples taken from the horn bud region were performed. Additionally, saliva cortisol concentrations were measured before and after intervention. Significant differences in horn growth were found between isoeugenol treatment and control group (P = 0.001), between clove oil treatment and control group (P = 0.001) and between thermal dehorning and control group (P < 0.001). After clove oil injection 10/10 calves showed signs of inflammation and swelling of the horn bud region including the upper eye lid area. CT images of animals after thermal disbudding showed complete destruction on the horn buds but also severe local damage to the frontal bone. CT images of animals after clove oil or isoeugenol injection showed complete or partial destruction of the horn bud. Histological examination was performed at 1 horn bud per animal of 5 per each group. Eight biopsy samples showed normal unchanged epidermis and dermis (3 isoeugenol, 5 control group), in 6 samples normal vital skin side by side with necrotic epidermis and/or dermis was found (2 isoeugenol, 2 clove oil, 3 thermal dehorning). In one sample (thermal dehorning) necrotic bone with osteomyelitis was detected. In 3 samples (thermal dehorning) dystrophic calcification was present. After clove oil treatment necrotic epidermis and dermis as well vital skin with a purulent crust was detected. The highest mean cortisol value was measured in calves treated with clove oil. Fifteen minutes after treatment the mean value of thermal dehorned calves showed the lowest values, however these calves were sedated for the treatment. Thermal disbudding tended to have the highest efficacy of disbudding. Horn growth was also substantially decreased in clove oil and in isoeugenol group. In cases in which the horn growth was not totally suppressed the horns remained very small. Based on our results, disbudding calves with isoeugenol causes less tissue damage than thermal disbudding. Since clove oil caused temporary swelling we consider it less suitable. Future research is required to evaluate the behavioral responses of calves experiencing these methods of disbudding; in addition, more research is needed to optimize the injection volume and technique in a larger group of animal.