Stress responses of wapiti (Cervus elaphus canadensis) to removal of velvet antler

Abstract

An assessment of stress responses of 27 mature wapiti (Cervus elaphus canadensis) stags was conducted to test the efficacy of two methods of analgesia to reduce stress responses associated with the pain of cutting velvet antler. Analgesic methods were a Lidocaine nerve block (LIDO) and pedicle placement electrical analgesia (EA). A control group of animals (CON) was included that did not receive analgesia. Methods of assessing stress responses included heart and respiration rates, differential white blood cell counts and plasma cortisol. Assessment of stress responses also utilized infrared thermographic imaging and measurement of salivary cortisol concentrations. The latter measures were novel approaches to stress assessment in wapiti, and, as such, the study was a trial of their applicability. Measures were conducted over 2 d. Antler was harvested on day 1 and the animals were brought back to the handling facility 24 h later (day 2) for repeated measures. Heart and respiration rates were increased in response to cutting antler (P < 0.05) and declined following antler removal (P < 0.003). Reductions in eosinophils occurred over a 24-h period in all treatments and were statistically significant for the EA treatment (P < 0.014). Plasma cortisol concentrations did not demonstrate statistical differences between either treatments or days. Plasma cortisol concentrations were numerically higher for the EA animals on days 1 and 2 than for either the CON or LIDO treatments. Plasma cortisol levels tended to be higher after capture and restraint on day 2 compared to levels recorded after antler removal on day 1. Salivary cortisol levels were higher on day 2 compared to day 1 (P < 0.004). Between treatments, CON animals exhibited higher salivary cortisol levels on day 2 than EA (P < 0.05) and LIDO (P < 0.002) animals. Radiated heat loss, measured by infrared thermography, was significantly elevated in response to velveting (P < 0.00001). Increased radiated heat loss was observed for all treatments and was statistically significant for EA (P < 0.006) and CON (P < 0.02), but not for LIDO (P < 0.06). The study demonstrated that the process of harvesting velvet antler from wapiti initiates a significant stress response similar to that of other animals during practices such as capture, handling and restraint. The data further suggest that stress responses to the above husbandry practices are exacerbated by the pain of cutting antler and that animals treated with Lidocaine for pain management exhibited a lesser stress response than CON or EA treated animals. Key words: Wapiti, velvet antler, analgesia, stress, salivary cortisol, infrared thermography