Sedating calves during disbudding slows their growth and may compromise welfare, new research from the Royal Veterinary College has revealed.
Disbudding — the removal of horn buds to prevent horn growth — is routine in the UK, carried out on hundreds of thousands of calves each year to reduce risks to handlers and other animals.
The procedure is painful and can take up to nine weeks to heal. In recent years, more farmers have turned to “knockdown” disbudding using the sedative xylazine, believing it makes handling easier and the process less stressful for calves.
Until now, however, little has been known about the wider impact of sedation. Between April and August 2024, RVC researchers monitored the disbudding of 485 calves on a Somerset farm, working with Synergy Farm Health and a large calf rearer.
One group of calves was given local anaesthetic and anti-inflammatories without sedation. The other received the same pain relief alongside xylazine sedation.
The study found sedated calves grew on average 0.14 kg per day less than non-sedated calves in the 20 days after disbudding.
Growth was slowest among animals given lighter sedation, while almost one in five calves showed movement during the procedure — suggesting sedation quality was inconsistent.
Researchers warned the findings raise both economic concerns for farmers and potential welfare issues for calves. Reduced weight gain could signal stress or delayed recovery.
Dr Sophie Mahendran, lecturer in farm animal welfare at the RVC, said: “The use of sedation for disbudding calves is becoming very common practice, so understanding the effects that xylazine use has is important.
"This work has shown that it causes reduced calf growth rates for approximately 20 days following disbudding, and that this effect was worse in calves that only experienced a light plane of sedation.”
She added that vets should consider whether sedation ought to be used routinely, or whether “investment into appropriate calf handling facilities should be encouraged on farms”.
The RVC team said more research is needed to explore any longer-term effects of sedation during disbudding on growth and calf health.
