Meeting Abstract
Studies suggest that, in animals, personality type is correlated with the degree of stress responsiveness. For example, white laying hens are reactive, flighty, and exhibit large hormonal and behavioral responses to stress while brown laying hens are proactive, exploratory, and exhibit low hormonal and behavioral responses to stress. The objective of this study was to determine if personality type also corresponds to differences in immune responses and to test additional measures of stress as well. To test the responses of the hens to stress, we provided feed according to an unpredictable schedule for 14 days, and measured corticosterone levels, heat shock protein expression, H:L ratios, and tonic immobility responses. We predicted that white hens would show greater stress reactions to the stress treatment. Plasma corticosterone levels were significantly greater after 7 days of treatment (p < 0.001), but did not differ significantly between strains. H/L ratios, on the other hand, were significantly elevated by day 14 of treatment (p < 0.04), and raised significantly more in white hens than brown (p = 0.03). After the stress protocol was completed, we then challenged hens immunologically. Immune function was assessed by comparing the febrile responses to lipopolysaccharide (LPS) injection and measuring two consecutive inflammatory responses to injection with phytohemagglutinin (PHA). Because white hens are exposed to more corticosterone in response to stressful stimuli, we predicted that brown hens would show greater immune responses than white hens. Swelling of the toe web in response to PHA injection was significantly greater in white hens than brown after both challenge events (p = 0.0003 and 0.008). Finally, LPS injection resulted in a significant increase in temperature at 6 and 12 hours post injection (p = 0.0001 and p = 0.02) in both strains but there was no difference between strains. Our results suggest that white hens are more reactive not only behaviorally and hormonally, but also immunologically.
