Surface temperature elevated by chronic and intermittent stress

Abstract

Stress in homeothermic animals is associated with raised body core temperature and altered patterns of peripheral blood flow. During acute stress, peripheral vasoconstriction causes a short-lived drop in surface temperature that can be detected non-invasively using infrared thermography (IRT). Whether and how skin temperature changes under chronic stress, and hence the potential of IRT in chronic stress detection, is unknown. We explored the impact of withdrawing environmental enrichments and intermittent routine handling on long-term skin temperature in laying hens (Gallus gallus domesticus). Immediately following enrichment withdrawal, comb, face and eye temperature dropped, suggesting this was acutely stressful. In the 3 weeks that followed, barren-housed hens displayed behavioural markers of frustration. Whilst control birds, housed in enriched conditions, showed a decline over weeks in both comb temperature and baseline corticosterone levels, barren-housed hens had no change in comb temperature and an increase in corticosterone. By the trial end, comb temperature (but not corticosterone) was significantly higher in barren-housed hens. This change in parameters over time may reflect cumulative impacts of enrichment withdrawal in barren pens and/or, as hens were young and maturing, age-related changes in controls. Comb, face and eye temperature were also higher on days following routine handling, and comb temperature higher on other days in hens that were regularly handled for blood sampling than for a less intensive weighing protocol. Together, these data support comb, face and eye surface temperature increase as a long-term marker of stress exposure in laying hens. It is important to recognise that the strength and even direction of these effects may vary with thermoregulatory and energetic context. However, in laboratory and indoor-reared farm animals that live in carefully managed environments, IRT of the skin can potentially be used to non-invasively monitor chronic and intermittent stress exposure.

Evidence that stress-induced changes in surface temperature serve a thermoregulatory function

“…Others, however, have contested this hypothesis by failing to substantiate immune-mediation of core temperature responses to stress (Long et al, 1990b, Soszynski et al, 1998; Hiramoto et al, 2009; Vinkers et al, 2009). At the level of surface tissues, however, a functional role of stress-induced changes in temperature, per se , appears yet to be raised (though breifly discussed in Herborn et al, 2018). Indeed, dominant theory explaining stress-induced changes in surface temperature posits that this phenomenon is merely a consequence of haemetic redistribution (Jerem et al, 2015; Jerem et al, 2018, Nord and Folkow, 2019) and holds no direct functional role; rather, it is haemetic redistribution, but not thermal modulation, that carries functional significance by attenuating blood loss in the event of injury (as long-shown following hemorrhage in McGuigan and Atkinson, 1921; Freeman, 1932; Darlington et al, 1986).…”

“…An effect of Ta on stress-induced changes in skin temperature suggests that the function of this phenomenon extends beyond haemetic redistribution and may provide thermoregulatory advantages, where heat conservation at low Ta (sub-thermoneutral) is enhanced during perception of environmental challenges. Supporting a thermoregulatory function to stress-induced changes in surface temperature, Herborn et al (2018) described an increase in skin temperature of Domestic Chickens ( Gallus gallus ) after exposure to chronic stress treatments at constant, thermoneutral temperatures, with respect to controls. Given exposure to stressors is thought to elevate metabolically generated heat (i.e.…”

“…as a consequence of tachycardia, tachypnea, and avoidance behaviour; Cabanac and Aizawa, 2000; Cabanac and Guillemette, 2001; Greenacre and Lusby, 2004; Long et al, 1990a), elevation of skin temperature under chronically challenging environments may facilitate dissipation of excess metabolically-generated heat, thereby reducing thermal load associated with activation of a stress response. Neither Nord and Folkow (2019), nor Herborn et al (2018), however, tested patterns of heat conservation or dissipation following stress exposure, rendering such thermoregulatory consequences of surface temperature responses speculative.…”

A temperate endotherm trades thermoregulation for self-preservation: stress-induced changes in surface temperature as thermoregulatory trade-offs

“…Additionally, in some studies, both skin temperature and superficial blood volume have been shown to rise following stress exposure (e.g. at the ears of Domestic Rabbits, Oryctolagus cuniculus , and wattles of Domestic Chickens, Gallus gallus ; Herborn, Jerem, Nager, McKeegan, & McCafferty, 2018;Yokoi, 1966) rather than fall. Such trends directly contrast the hypothesis that stress-induced thermal responses are merely functionally neutral corollaries of blood-loss mitigation strategies.…”

Vascular response to social cognitive performance measured by infrared thermography: A translational study from mouse to man

“…The autonomic nervous system response during such social interactions—highly conserved across mammals and perceived like “stress”—leads to altered vasoactivity in peripheral and core body regions. The resulting blood flow changes via vasoconstriction and vasodilation, respectively, affect local body temperature . Exposure to an embarrassment task, for instance, led to an increase in facial blood flow in both male and female participants, measured via Laser Doppler Flowmetry .…”