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Evaluation of a disposition scoring system in pen-raised white-tailed deer
Pen-raised white-tailed does (n=63) ranging in age from 1.5 yr to 6.5 yr were utilized to evaluate the accuracy of a subjective disposition scoring system for deer by assessing the physiological response to restraint through measurement of serum cortisol concentration. Does were administered annual vaccinations and dewormer while restrained in a drop-floor chute designed for whitetail deer. Following processing and prior to being released from the chute, blood samples were obtained via jugular venipuncture and serum was harvested to determine cortisol concentration by RIA analysis. Disposition scores ranging from 1 to 5 (1 = docile and 5 = aggressive) were also assigned by independent observers to evaluate deer behavior while restrained in the chute. Pearson correlation coefficients were used to determine the relationship between cortisol concentration and disposition scores, and a one-way ANOVA was utilized to determine if differences existed among mean cortisol concentration for each of the disposition scores. A moderately positive relationship (r = 0.30, P<0.02) existed between disposition score and serum cortisol concentration; however, there was no difference in mean cortisol concentration for does receiving a score of 1, 2, 3, or 4 (56.0, 69.7, 69.3, and 54.0 ng/mL, respectively). Does that received a disposition score of 5, indicating the most aggressive behavior while restrained in the chute, had a greater (P<0.01) mean serum cortisol concentration (118.8 ± 13.1 ng/mL) when compared to does receiving a lower numerical disposition score. These results indicate that the disposition scoring system accurately identified does undergoing the greatest physiological stress while restrained in a working chute, but the scoring system requires modification in order to accurately assess lower levels of stress associated with scores 1 through 4 of the system.
Keywords:
deer, stress, disposition