The effects of the treatment, hospitalisation experience, and possible side effects are rarely a consideration; yet, may negatively impact welfare to a greater extent than the medical condition itself. The five freedoms are often parameters used to measure welfare. However, the absence of pain, hunger, fear and distress, etc. is not indicative of good welfare and positive experiences, merely the lack of negative experiences.
Affective experiences are subjective states that cannot be measured directly in animals; therefore, there is a major knowledge gap in the assessment of emotional states in animals. Many behavioural and physiological tests exist to measure welfare but are not feasible in the veterinary practice environment and a major caveat is that these tests show emotional arousal, not emotional valence (i.e. positive or negative affective state). Moreover, in companion animals such as dogs, tests cannot be standardised due to the variation in previous experiences and individual differences. Thus, reliable methods of measuring positive affective states are essential to infer good welfare.
One method that has proven to be a useful tool in measuring a physiological response to stress is infrared thermography (IRT). When an animal becomes stressed, the hypothalamic-pituitary-adrenal (HPA) axis is activated (Zamora-González et al. 2013), resulting in sympathetic mediated peripheral vasoconstriction to divert blood from the periphery to the core organs (Stewart et al. 2005). This causes surface temperature to drop and an increase in core temperature, which is termed stress-induced hyperthermia. Thermal imaging works by detecting naturally emitted thermal irradiation and enables cutaneous temperature recordings to be measured. By detecting these changes in temperature, IRT has become a useful tool in measuring subtle changes in affective state. An intrinsic benefit to IRT is that it is non-invasive. Many other physiological indicators of stress such as cortisol measurement and core temperature require invasive techniques to obtain, which are not practical in veterinary practice and may result in an increased stress response confounding the welfare assessment.
Behaviour is an alternative measure of welfare; however, unless you know the patient well, behavioural indicators of stress are not always reliable due to factors such as individual variability (sex, breed, personality, environment, previous experience, etc.). Therefore, a physiological measure such as IRT alongside behaviour will likely provide more accurate results when measuring welfare states in veterinary inpatients.
A number of studies have evaluated the use of IRT as a measure of affective state in a number of species, including dogs (Vianna & Carrive, 2005; Jerem et al. 2015; Travain et al. 2015; Foster & Ijichi, 2017).
The available literature highlights that the region of interest used to measure surface body temperature can increase or decrease depending on the anatomical region measured and the investigated species. In dogs, eye (lacrimal caruncle) temperature is reported to indicate general arousal; however, ear temperature has been shown to differentiate between positive or negative affective states in dogs (Riemer et al. 2016). During negative emotional states, pinna temperature will decrease from baseline, and when experiencing positive affective states, temperature will increase from baseline.
IRT can be easily implemented into the veterinary practice as a measure of welfare. Basic thermal imaging cameras start from approximately £200 and more advanced cameras up to £80,000. The FLIR ONE PRO® camera is a small device that is attached to smartphones and the FLIR C2® is a small portable camera; both are inexpensive and have a thermal sensitivity of <0.1°c. Most thermal cameras have video functionality; this allows both real time measurements and long-term recording to assess welfare over time.
To measure surface temperature of the pinna, a spotmeter can be used. The spotmeter on the camera screen is simply pointed at the apex of the pinna and the temperature is displayed. The colour palette of the image can also be changed to easily visualise temperature differences (Figure 1). This provides us with instantaneous results to assess whether the dog is in a positive (increase from baseline) or negative (decrease from baseline) emotional state during or following a procedure, veterinary consultation etc.
Another potential benefit of IRT is that ear temperature is reported to be a reliable indicator of core temperature; therefore, IRT may also be used as a non-invasive alternative measure to rectal temperature (Zanghi, 2016). However, further research is needed to validate this.
A drawback to the use of IRT in companion dogs is that ears that are fluffy or excessively hairy will need to be shaved. Consent will need to be obtained from owners to shave regions of their dogs; however, this should be acceptable to most owners if we manage their expectations and explain it will allow us to monitor how their dog is feeling.
An additional disadvantage to IRT is that thermal radiation is reflected and does not penetrate through transparent plastic or glass. If dogs are hospitalised in transparent kennels, doors will need to be opened to obtain readings; however, this may confound the measurement by causing a change in the dog’s emotional state.
Despite this, the increasing amount of evidence presents promising results, and IRT is likely to be a useful tool in the assessment of animal welfare. Further research is being conducted to assess the use of IRT as a valid tool in the measure of welfare and affective state in dogs.
Animal Welfare Assessment Grid
The Animal Welfare Assessment Grid (AWAG) is a validated tool that monitors the welfare of animals and is highly adaptable to any species. The system was developed by the University of Surrey, School of Veterinary Medicine in collaboration with Public Health England. The AWAG assesses physical health, psychological wellbeing, environmental comfort, and veterinary and management procedural events. The tool encompasses the five domains of animal welfare and draws attention to the temporal component of welfare that is often overlooked (Wolfensohn et al. 2018).
Each parameter (physical, psychological, procedural and environment) is subdivided into a number of factors that contribute to the overall score. For example, the physical score would encompass the patient’s general condition, clinical assessment, pain control, inappetence, activity level etc.
Within each parameter, various factors are scored between one and ten. Each factor score is defined using descriptors for each number to reduce scoring bias. A score of one indicates the best possible state (lowest possible impact on welfare), whilst a score of 10 would be the worst possible state (highest possible impact on welfare), for each respective factor. For each parameter, mean factor scores are calculated and this allows the clinician to ascertain what parameters are impacting quality of life at that time-point (Wolfensohn et al. 2015)
In addition to the ability to quantify quality of life at a given time-point, the tool provides a visual representation of the animal’s welfare state. The axis displays the four parameters. Each factor score is calculated, and the relevant scores are marked on the x and y axis. These points are joined together to create a polygon and the total area covered is calculated to derive a cumulative welfare score at that particular point in time (Figure 2).
If significant changes in welfare are seen, the tool can show which factors have contributed to these changes and intervention can be undertaken to improve the animal’s wellbeing. This is particularly important in hospitalised patients as it allows veterinary staff to assess the welfare impact of clinical interventions and environment, as well as physical and emotional health to determine what factors are influencing welfare. Veterinary staff can then enhance the factors that contribute to positive welfare and reduce or change elements that are negatively impacting welfare. The AWAG represents a valuable tool for veterinary professionals as it equips vets with a valid, fast, non-invasive, objective measure of welfare. The tool is currently being further developed to strengthen the transferability of AWAG to as wide a field of experimental disciplines as possible, and to incorporate additional features. Developments include: improving the ease of installation and setup of the software, making it more accessible for individual users and small companies, updating the user interface to ensure maximum usability, while providing an intuitive, user-friendly layout (NC3Rs 2018). As the majority of staff in veterinary practice have smartphones or access to tablets, the AWAG is easily accessible for veterinary staff.
In summary, both infrared-thermography and The Animal Welfare Assessment Grid are proving to be promising, novel tools in the assessment of positive and negative welfare states in dogs. Utilising instruments that can reliably demonstrate the affective state of patients, and furthermore, establish the factors influencing welfare in individuals, will help to improve the experiences dogs have in the veterinary practice.