Introduction
In the veterinary profession we tend to consider welfare mainly in terms of the physical state of an animal. When we consider human welfare or 'quality of life,' however, there is much greater emphasis on how we 'feel' about things, and, similarly, animal welfare science focuses on the subjective state of individual animals. Dogs have an anatomically similar limbic system in the brain and a physiologically similar response to anxiolytic drugs, so it can be assumed that they experience "feelings" in some form, as we do. But, as these emotional responses are 'internal,' they are inevitably much harder to assess objectively. Over the past two decades, considerable progress has been made in devising methods for assessing the welfare of many domestic species. However, many difficulties remain in both measurement and interpretation - particularly for the domestic dog which is arguably the most complex domestic species in terms of their welfare requirements, because of differences in response due to breed, individual differences, and previous experiences.
Approaches to Welfare Measurement
There are two main approaches to considering the welfare status of the domestic dog within a specific context, such as kennels. These are:
To consider those features of the species, such as its natural behavioural repertoire, in order to ascertain which aspects of the environment are likely to influence its welfare.
By looking at various parameters related to the individual animal, such as its behaviour and physiological state, and use these to assess to what extent the individual is coping with the environment in which it finds itself.
Both of these approaches have advantages and disadvantages. For example, the measurement of individual behavioural parameters can be problematic due to large individual differences in learnt behavioural strategies. It is also difficult to identify exactly what constitutes a 'natural behaviour' when considering a domesticated species.
Physiological measures of the stress response in individual animals have the advantage that they are quantitative: a value is obtained that can be compared with values obtained in different conditions or from other individuals. However, not only is there huge individual variation in physiological response to stressors, but also there are normal variations at different times of day that can make comparison and interpretation difficult. Measurable physiological parameters do not co-vary, and there are often problems in measurement of parameters because animals must be habituated to sampling or measuring techniques to ensure that it is not these processes themselves that are causing changes in the stress response. In addition, some measures have the disadvantage of requiring invasive sampling methods.
Welfare Assessment of the Domestic Dog
Assessment of welfare in the dog is difficult for two reasons. First, the dog was the first species of animal to be domesticated, and its domestication has been a complex process that has resulted in many different types (herding, hunting, guarding, companion, etc.) with distinct behavioural repertoires as well as distinctive appearances. Thus, the visible signs of welfare status are likely to differ from one dog to another, both because their behavioural tendencies vary and because the signalling structures (ears, coat, tail, etc.) have been modified to different extents.
Second, if we can assume that the capacity to experience suffering evolved as an adaptation that was useful to the dog's wild ancestors, selective breeding for behavioural traits may have modified the original links between sensation, emotion, and behaviour, to the point where it becomes very difficult to predict when an individual dog might or might not be suffering.1 For example, very high thresholds for pain appear to have been bred into fighting dogs; probably through opiate receptor sensitivity or numbers, and this may well have an impact upon other emotional responses in these breeds. In herding breeds such as the collie, the internal organisation of predatory behaviour in the wolf has been modified through breeding and then training; and it may well be that such dogs feel more frustrated than others when prevented from responding to stimuli eliciting herding behaviour. The potential for breed-to-breed variations has, unfortunately, hardly been investigated, since the majority of studies that have been conducted have used beagles in laboratory kennelling.
Physiological and Behavioural Indicators in the Dog
In a series of studies conducted in the Netherlands,2-4 Beerda and coworkers have proposed a number of indicators of both acute and chronic welfare in such settings. Their physiological measures included heart rate, circulating catecholamines, circulating and urinary cortisol, immune status; behavioural measures included abnormal behaviour (stereotypies and repetitive behaviour, self-mutilation, coprophagy), behaviour indicating frustration (chewing, vocalising), conflict behaviours (body-shaking, paw-lifting), and a lowered fearful posture.
In animal welfare science, the general consensus is that multiple measures of welfare are almost invariably more informative than any single measure. However, given the behavioural diversity of the domestic dog, it could be argued that, except when dealing with single-breed groups, physiological parameters might be more informative than behaviour. The taking of samples for physiological measures can be stressful in itself, potentially confounding the information obtained, but cortisol can be measured from urine collected as part of the dog's normal husbandry and may offer a routine method for assessing welfare in kennelled dogs in a wide variety of situations. Several studies that attempt to validate urinary cortisol as an indicator of welfare in kennelled dogs of all types, have been conducted at the University of Bristol. For example, in two populations (one consisting of male Labrador retrievers and the other various gundog breeds) urinary cortisol increased on initial kennelling and increased less in individuals with prior experience of kennelling than in those without. However, there were no correlations between cortisol titres and behaviour. Many dogs altered their behaviour in the kennel as time progressed, but these changes may simply have been due to their learning which behaviours were effective in this unaccustomed situation, rather than being indicators of welfare per se. The initial effects of kennelling on behaviour appeared to be specific to the individual dogs and did not, unlike cortisol, reflect their prior experience of kennels.5
In dogs of a wide variety of breeds newly admitted to a rescue shelter, absolute levels of cortisol appeared to be uninformative.6 Titres tend to decrease with time, as also found by Hennessy and coworkers,7 indicating adaptation to the shelter environment, but only in dogs that had previously been in shelters. Urinary cortisol tended to increase in dogs that had come from domestic environments, possibly indicating a build-up of chronic stress. Drinking and grooming behaviour increased with time, and panting and pawlifting decreased, but none correlated with changes in cortisol titres, as previously found by Beerda and coworkers.8
Cognitive Measures of Welfare
To overcome some of the problems associated with behavioural and physiological welfare measures, new studies have started to develop alternative ways of 'asking' animals about their subjective state. Studies of humans show that people in a negative mood are more likely to attend to negative or threatening stimuli, remember negative events, and judge ambiguous stimuli or future events as being negative, than people in a more positive mood:9 their cognitions are biased in a negative way. Cognitive bias may thus be a good indicator of the valence (positive/negative) of a person's mood state, and there are also theoretical reasons for thinking that it may closely reflect a person's conscious experience of emotions. For these reasons, cognitive bias is a potentially valuable addition to the current indicators of animal emotion. Tests of cognitive bias developed in rats10 have been adapted for use in dogs11,12. Dogs are first taught that a goal in one location is consistently rewarded, whereas another location equidistant from the start box is not. Once this discrimination is learnt, dogs are offered a goal between the rewarded and unrewarded goal locations. Their latency to run to this new location is measured as an indication of whether they consider this novel goal as 'likely to contain food' ('optimistic') or not ('pessimistic'). Measures of cognitive bias in dogs have been found to correlate with dogs' response to social separation11,12 and also with different training methods, suggesting that this may be a useful approach in evaluating how dogs 'feel' about different environments.
Conclusions
Overall, these studies highlight the difficulties of reliably assessing the short-term or long-term effects of kennelling on the welfare of dogs, although interpretation is easier where the population is uniform and their background history fully understood. While physiological indicators appear to be more quantitative, results can be difficult to interpret, and further understanding of the relationship between stress and physiology is needed before they can be used to assess welfare in all circumstances. Novel measures such as 'cognitive biases' seem a promising new approach to welfare assessment, but interpretation can be difficult where multiple factors can influence subjective state.
References
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