Reynolds JP, Lehenbaue TW, Weibe BVeterinary Medicine Teaching and Research Center, University of California, Davis
Dehorning is a common procedure performed on young dairy calves. Recent studies have evaluated alleviation of pain associated with local anesthetics and specific nonsteroidal anti-inflammatory drugs (NSAID), ketoprofen and meloxicam, which are not approved for use in food animals in the United States. The objective of this study was to evaluate the effects of a local anesthetic and flunixin meglumine, an NSAID labeled by the FDA for use in livestock, for alleviating pain and distress caused by dehorning in young dairy calves. A group of 45 Holstein dairy calves (11 male; 34 female) were randomly assigned to one of three treatment groups prior to dehorning. The three treatment groups were defined according to the specific compounds which were injected around the horn bud (cornual ring block) and given as an intramuscular injection in the neck, respectively: saline for each type of injection (control); cornual ring block only - lidocaine hydrochloride and saline (LC); cornual ring block and NSAID - lidocaine hydrochloride and flunixin meglumine (LC+FM). Following injections, calves were dehorned with a propane-powered dehorner. After dehorning, calves were observed for 10-minute periods during intervals of 0-2 h, 2-4 h, and 4-6 h, for behavioral signs associated with pain (ear flicking, head shaking, head rubbing, tail flicking, vocalizing, and feed or water consumption). Additionally, venous blood samples were collected at 45 min prior to and 0.5 h, 1 h, and 3 h after dehorning and analyzed for cortisol concentration. Non-parametric statistical analysis of calf behavior data showed significant (P ? 0.05) advantages for calves in both the LC and LC+FM groups compared to control calves for each of the behaviors except head rubbing during the 0-2 h interval after dehorning. During the 2-4 h interval, calves in both LC and LC+FM groups had significantly less head shaking compared to controls. Additionally, the LC+FM calves had significantly increased feeding and drinking behaviors compared to controls. During the 4-6 h interval, control calves had significantly increased head rubbing compared to the other two treatment groups. The calves in the LC+FM group also had significantly less ear flicking and head shaking compared to controls. None of the comparisons between calves in LC and LC+FM groups was significantly different except for increased feeding and drinking activity exhibited by LC+FM calves during the 2-4 h interval. Results from cortisol assays are pending data analysis. Results based on observed behaviors in dairy calves following dehorning showed improved welfare outcomes for calves receiving either local anesthetic or both local anesthetic and NSAID compared to control calves. Pending evaluation of cortisol levels may help to provide evidence for the benefit of including flunixin meglumine in addition to a local anesthetic for alleviating pain in dairy calves following dehorning.