Pain and Pessimism: Dairy Calves Exhibit Negative Judgement Bias following Hot-Iron Disbudding

Abstract

Pain is defined as an unpleasant sensory and emotional experience associated with actual or potential tissue damage, but emotional states are difficult to directly assess in animals. Researchers have assessed pain using behavioural and physiological measures, but these approaches are limited to understanding the arousal rather than valence of the emotional experience. Cognitive bias tasks show that depressed humans judge ambiguous events negatively and this technique has been applied to assess emotional states in animals. However, limited research has examined how pain states affect cognitive processes in animals. Here we present the first evidence of cognitive bias in response to pain in any non-human species. In two experiments, dairy calves (n = 17) were trained to respond differentially to red and white video screens and then tested with unreinforced ambiguous colours in two or three test sessions before and two sessions after the routine practice of hot-iron disbudding. After disbudding calves were more likely to judge ambiguous colours as negative. This ‘pessimistic’ bias indicates that post-operative pain following hot-iron disbudding results in a negative change in emotional state.

The Psychology of Cows

“…Negative emotional states also appear to influence judgment abilities in dairy calves. Very young Holstein calves exhibited a negative judgment bias for at least 22 hrs after hot-iron disbudding; the calves were less likely to approach ambiguous screen colors in two sessions after the procedure (Neave, Daros, Costa, von Keyserlingk, & Weary, 2013). A second cognitive bias study investigated 13 mother-reared Holstein dairy calves' abilities to discriminate between red and white colors on a computer monitor.…”

Acute stress enhances sensitivity to a highly attractive food reward without affecting judgement bias in laying hens

“…For example, restraint in isolation (Doyle et al, 2010), unpredictable environments and shearing (Sanger et al, 2011) in sheep, disbudding in cattle (Neave et al, 2013) and unpredictable environments in rats (Harding et al, 2004) all result in shifts in the expectation of a positive (i.e. optimistic) or negative (i.e.…”

“…However, if the animal does not respond or the latency to respond is similar to that of the negative cue/location then the response is considered as being pessimistic. This type of test has been used to assess judgement bias in livestock including sheep (Doyle et al, 2010;Sanger et al, 2011;Destrez et al, 2012), pigs (Douglas et al, 2012), cattle (Neave et al, 2013) and poultry (Salmeto et al, 2011;Wichman et al, 2012) and most such tests are sensitive enough to detect differences attributed to the affective state of the animals. However, it has been argued that this type of task, where the only outcome measured is the latency to approach or not approach within a time limit, has limitations in its interpretation as negative affective states may be associated with a general reduction in activity and feeding motivation reflecting a response bias rather than a judgement bias (Brilot et al, 2010).…”

Limits to using HPA axis activity as an indication of animal welfare

“…They found that when a tone was played with a frequency close to or equal to 4 kHz, rats housed in unstable conditions were slower to press the lever than rats housed in stable conditions, which is consistent with a decreased anticipation of reward. This "pessimistic" judgment bias has since been demonstrated in a few other species (including humans) and situations (Brilot et al, 2010;Daros et al, 2014;Hales et al, 2014;Mendl et al, 2009;Neave et al, 2013;Papciak et al, 2013;Scheele et al, 2013;Verbeek et al, 2014). Conversely, Swan and Hickman (2014) …”