Pain management is important for optimal recovery and good welfare for all patients, including in equine practice. Horses are prey animals and are notorious for trying to hide signs of pain, so the accurate and careful assessment of the clinical signs of pain is essential for equine welfare. For registered veterinary nurses (RVNs) the ability to recognise the signs of pain in equine patients is essential. This article will discuss different pain scoring methods for use with equine patients.
Pain scoring in equine patients
The recognition and alleviation of pain is critical for the welfare of horses. As in other animal species, pain in horses is difficult to assess because of their inability to communicate with humans. This could be further compounded by horses potentially suppressing the exhibition of obvious signs of pain in the presence of possible predators such as humans (Dalla Costa et al., 2014).
The recognition and alleviation of pain is critical for the welfare of horses. As in other animal species, pain in horses is difficult to assess because of their inability to communicate with humans
Several behaviour-based assessments of pain in horses have been devised. Specific pain scoring systems have used the inclusion of multiple pain-associated parameters. These take the form of composite pain scales (CPS) and include the measurements of selected “items” that may include interactive, behavioural and physiologic parameters (Lawson et al., 2020). CPSs are multifactorial scales where the measured “items” are scored according to a simple descriptive scale, and these scores are then combined to generate a CPS score. All published studies describing various CPS systems in the horse have demonstrated an excellent inter-observer reliability (Lawson et al., 2020).
In humans, facial expressions are routinely scored both manually and automatically using the Facial Action Coding System (FACS), which is considered an accurate and reliable method that describes the changes to the surface appearance of the face resulting from individual or combinations of muscle actions, referred to as “action units” (Dalla Costa et al., 2014). Action units relating to pain have been identified in rodents and rabbits and incorporated into species-specific “grimace scales”. The Horse Grimace Scale (HGS) devised by Dalla Costa et al. (2014) may offer an effective and practical method of identifying painful conditions. The HGS incorporates six facial action units (FAUs) that are independently scored (Box 1).
Each FAU is scored from images on a 3-point scale, with 0 indicating that the assessor is confident that the action unit is not present, 1 indicating that the assessor is confident that the action unit is only moderately present and 2 indicating that the assessor is confident that the action unit is obviously present. The HGS has been shown to be a potentially valid measure of pain following routine castration surgery (Dalla Costa et al., 2016). Figure 1 shows a horse demonstrating typical facial expressions associated with pain.
Consideration for different types of equids is also important. The donkey is a stoic animal and rarely displays readily visible signs of pain, distress or fear (Evans and Crane, 2018). It is therefore essential that both RVNs and vets working with donkeys can accurately assess pain and treat it accordingly (Box 2).
The reliability of assessing pain using facial expressions alone has been questioned (van Loon and Macri, 2021). However, facial expression pain scales can be applied in association with CPSs to enhance the assessment of pain in horses and donkeys.
Factors affecting pain scoring and assessment
Coat colour can also influence pain scoring. Dalla Costa et al. (2014) found that dark horses were often more difficult to score than those with lighter coats, especially if the background was dark. This effect could have been increased during the Dalla Costa et al. (2014) study, as images were being assessed. In practice, the pain score would more likely be assessed by observing the patient directly. However, the effect of coat colour should still be considered by vets and RVNs carrying out pain scoring.
Little attention has been paid in the existing pain scales to the influence of personality, stress or coping style on pain in horses (van Loon and van Dierendonck, 2018). It may be reasonable to suggest that different breeds may require individual grimace scales. For example, Thoroughbred horses are generally more expressive when it comes to pain, in comparison to more stoic breeds such as a cob. There will be individual variations within breeds, however, and this is where an assessment of patient personality is important.
RVNs could be an important asset when it comes to objective pain scoring due to their close relationship with the patients
RVNs are in a unique position to make these assessments. RVNs tend to spend increased amounts of time with patients, whether that be making a clinical assessment, grooming or generally observing them in the hospital environment. RVNs could be an important asset when it comes to objective pain scoring due to their close relationship with the patients. Furthermore, this also highlights the importance of talking to owners about the individual patients, what they like and dislike, to get an idea of personality and behaviour. Again, RVNs are in a good position to gain this information during the admit procedure. This also shows the owner that their horse or donkey will receive individualised care and treatment, which will hopefully lead to a sense of comfort and trust in the practice.
Implementing pain scoring in practice
There are many different methods available in practice to pain score equine patients; however, implementing pain scoring can be difficult. Initial introduction of the new ideas can be met with scepticism and resistance. One way to address this is to introduce the idea at a meeting and allow the whole team to have their say. Different pain scoring methods could be presented at the meeting, but it should be up to the veterinary team present to select an accurate method that will work moving forward in the individual practice in question. If every team member can put ideas forward, they will feel more invested in the process, which will ultimately increase compliance. This in turn will contribute to the welfare of the equine patients at the practice.
Initial introduction of the new ideas can be met with scepticism and resistance. One way to address this is to introduce the idea at a meeting and allow the whole team to have their say
Conclusion
There are many different methods available to assist veterinary professionals to pain score horses in practice. The method selected should be one that is accurate, and easy to use in practice. Vets and RVNs should both be involved in pain scoring patients, considering different factors such as species, breed, personality and the coat colour of the patient in question. With inter-team collaboration, pain scoring can be assessed and developed to increase the welfare and recovery of equine patients being treated in veterinary practice.
