September 2021
By Brad Heins and Hannah Phillips
Dairy calves commonly experience painful disbudding procedures as a part of the standard of care. Approximately half (52%) of pre-weaned dairy calves are disbudded prior to 8 weeks of age, but only 28% of disbudded calves are given pain mitigation therapies for the procedure. Furthermore, a survey of 189 organic dairies in the US indicated that only 26% use a local analgesic, non-steroidal anti-inflammatory drug or sedation to relieve pain related to horn removal procedures. Organic-approved options for pain management are limited to substances approved by the USDA National Organic Program. However, even those permitted by the National Organic Program face barriers to common use, such as opposition by farmers, difficulty of administering and a lack of Food and Drug Administration approval for use in cattle. Despite this reluctance to implement pain alleviation methods, some organic farmers have expressed interest in or currently implement plant-based alternatives.
The most popular pain management method is lidocaine injected as a cornual nerve block. Although lidocaine reduces pain and stress, it may be an obstacle for some producers. Lidocaine must be injected into the cornual nerve, which is very close to the eye, the injection itself causes pain, and calves feel pain once the numbing effect dissipates. There has been recent consumer and producer interest in natural, noninvasive treatments, leading producers to consider using herbal medicine. However, there is little research on the effectiveness of herbal-based medicine.
White willow bark has shown to be a useful analgesia in humans, and its utility to alleviate pain in calves remains of interest, especially for organic dairy producers. Commonly, white willow bark is used in combination with other medicinal herbs and analgesics to alleviate inflammatory pain in disbudded calves under organic management, but there is no evidence on whether white willow bark has any effects on inflammation in calves. At the University of Minnesota West Central Research and Outreach Center dairy in Morris, MN we wanted to assess the effects of intravenous flunixin meglumine injection (Banamine®) and 3 oral doses of white willow bark on inflammation and salicylic acid concentrations in healthy calves.
We used 25 crossbred bull calves for the study and seven days prior to the study, calves were acclimated to handling and restraint before disbudding. During each of 2 treatment periods, calves were assigned to receive either 57.6 mg/kg oral white willow bark (LOW), 115.1 mg/kg oral white willow bark (MED), 230.3 mg/kg oral white willow bark (HIGH), 2.2 mg/kg i.v. flunixin meglumine (FM) or no treatment (NT). Flunixin meglumine lowered inflammation (see Figure), while the white willow bark was ineffective at reducing inflammation and achieving a minimum plasma salicylic acid concentration necessary for analgesia in calves.
The estimated amount of salicin needed to achieve analgesia in calves is quite large considering that white willow bark has a minute amount of salicin. Even if a standardized white willow bark extract, such as a 15% salicin product was used, it would have to be given at a total dose of approximately 6,933 to 9,707 mg/kg (equivalent to 1,040 to 1,456 mg/kg of salicin). This dose could potentially be given over 1 to 3 days in drinking water or milk as demonstrated with aspirin in other studies. However, this method may be impracticable considering time and financial constraints. Furthermore, there is currently no evidentiary support on whether white willow bark at high doses given over several days has any effect on inflammation in calves. Results of this study indicate that the white willow bark doses used in this experiment are unsuitable for producing analgesia in calves. Flunixin meglumine lowered inflammation, while the white willow bark was ineffective at reducing inflammation. In the future, this research project will look at additional alternative methods for disbudding and pain management and provide scientific evidence to producers.