Effects of Willow Bark (Salix Extract) on Pain and Stress Following Disbudding of Organic Dairy Calves

Cautery disbudding is a painful procedure and major welfare concern in organic dairy production, which lacks effective and easily implemented methods of pain control. Willow bark (WB) has been used to treat chronic pain in humans, but there is no scientific evidence that WB has an analgesic effect in dairy cattle. The objective of this study was to evaluate the effect of an oral WB bolus on heart rate, salivary cortisol concentration, ocular temperature, and lying behavior (time, bouts, and bout duration) of 42 Holstein and crossbred calves. Heifer calves were born at the University of Minnesota West Central Research and Outreach Center, Morris, MN organic dairy. Calves were disbudded from 4 to 7 weeks of age (42 ± 3 d) and randomly assigned to one of three treatments (n = 14 calves/treatment): hot iron disbudding with lidocaine (LID; 5 mL per horn bud), hot iron disbudding with oral WB (200 mg/kg), or sham disbudding (SD). Saliva samples and thermal images were collected 1 h before disbudding, at disbudding, and 5 min, 10 min, and every 30 min until 240 min after disbudding. Cardiac monitors recorded heart rates continuously throughout the 5 h study period. HOBO loggers recorded lying behavior during the 72 h following disbudding. The variables included in the statistical model for analyses were fixed effects of treatment, time, and the interaction between treatment and time, and calf was a random effect. The mean heart rate of LID calves (123.3 ± 2.8 beats/minute) and WB calves (124.5 ± 3.2 beats/minute) were higher than SD calves (110.8 ± 2.3 beats/minute). Salivary cortisol concentrations were higher for the LID calves (103.8 pg/mL) and for the WB calves (103.4 pg/mL) than for the SD calves (85.5 pg/mL). The ocular temperature was not affected by treatment group. There were fewer lying bouts 24 to 48 h after disbudding compared to the first 24 h after disbudding in both the LID and WB treatment groups. Treatment group did not affect lying time or lying bout duration. Neither LID nor WB alleviated the pain of calves throughout the post-disbudding period. The results highlighted the need to discover suitable options for pain mitigation of calves in organic livestock production.