This study assessed the effects of flunixin meglumine (FM) and a local anesthetic block (LA) on postcastration performance, plasma cortisol concentration, and behavior in dairy calves. Thirty 2- to 3-mo-old Holstein-Friesian bull calves were allocated to 5 treatments: castration with LA (2% lidocaine injected into the testes and subcutaneously), castration with FM (1.1mg/kg, i.v.), castration with LA+FM, castration without drugs (CC), and sham castration (SC). Castration was performed using a Newberry knife and Henderson castrating tool. Feed intake and body weight gain were recorded for 10d postcastration. Plasma cortisol concentration and behavior frequency and duration were monitored for 8h postcastration. Variables with repeated measures were analyzed using PROC MIXED (SAS Institute Inc., Cary, NC); one-way ANOVA was used for nonrepeated measures. No differences in feed intake or body weight gain were detected among groups. Calves in the CC, LA, and FM groups had transient (<60, <60, and <45 min, respectively) increases in plasma cortisol concentration after castration, with a second increase at 120 min in the LA group, whereas cortisol concentration remained at baseline in the LA+FM and SC groups. Mean cortisol concentrations were lower for calves in the LA+FM and SC groups than in the CC group. The area under the plasma cortisol concentration curve during the first 3h postcastration was greater in CC- and LA-treated calves than in SC controls. Castration without drugs was associated with higher frequencies of crouching and statue standing and less oral activity compared with SC controls. Administering LA alone before castration was associated with higher frequencies of head turning, statue standing, and postural changes, and less feeding behavior compared with SC controls. More leg lifting to groom was seen in LA+FM-treated calves than in SC controls. Calves administered FM alone before castration exhibited less crouching than CC calves, fewer postural shifts, and more feeding behavior than LA-treated calves. In summary, FM alone tended to shorten the duration of cortisol response and reduce crouching after surgical castration. Combining LA+FM eliminated the cortisol response to castration but was associated with more leg lifting behavior. Treatment with LA alone did not mitigate the cortisol response and was associated with several behavioral differences compared with SC, FM-treated, or FM+LA-treated calves. Results suggest that LA alone did not effectively control discomfort in young dairy calves castrated using the Henderson castration tool.

Dairy calves and early-weaned beef calves are often weaned at 2-3 months of age and castrated at that time. Most studies examining the effects of analgesic and anesthetic agents on responses to castration focus on older or younger cattle. Also, no analgesic or local anesthetic agents are approved for reducing castration-associated pain in calves in the US. Extra-label use of such agents should be based on evidence of efficacy. Our objective was to provide tangible data on the effects of flunixin meglumine (FM) and local anesthesia (LA) on cortisol and performance responses associated with surgical castration in 2- to 3-month-old dairy calves.

US dairy calves are often disbudded at an early age without analgesics, whereas several other countries require analgesics. Administration of nonsteroidal antiinflammatory drugs (NSAIDs) in milk replacer would be a simple, stress-free method to deliver analgesics for disbudding if shown to improve well-being. Most studies of NSAID efficacy involve older animals, NSAIDs not labeled for use in US cattle, or NSAIDs administered by injection. Our objective was to determine the effects of administering an NSAID labeled for use in US cattle (flunixin meglumine; FM) in milk replacer on heart rate (HR), physical activity (PA), and salivary cortisol concentration (SCC) in young dairy calves disbudded by cautery.