Proceedings: Animal Welfare: from Science to Law

Legally accepted pain and other poor welfare in animals

by Pr Donald M. Broom

Centre for Animal Welfare and Anthrozoology, University of Cambridge, U.K.

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To cite this article (suggested): Broom D.M., « Legally accepted pain and other poor welfare in animals » [PDF file], In: Hild S. & Schweitzer L. (Eds), Animal Welfare: From Science to Law, 2019, pp.165-174.

Summary

Animals kept as pets or for farming, including all mammals, birds and fish, have pain systems and their welfare can be poor because of pain or fear. The extent of pain can be measured using physiological and behavioural measures such as thermography or grimace scales in sheep, horses and mice. It is important to evaluate the magnitude of poor welfare, a function of severity and duration.

In general, our laws prohibit treatment of animals that causes pain or other poor welfare. However, there are exceptions in laws for reasons of tradition, financial cost, gastronomic preference, convenience in management or breeding, or avoidance of other problems. Some activities that harm animals are considered to be “sport”. For example the bull pierced by numerous lances in the corrida, the deer chased by dogs and by humans on horseback, or the dog or cock forced to fight. These “sports” have entirely negative effects for the animal. Another example is the animal killed during shechita or halal slaughter without prior stunning. The justifications for this are: tradition, edict from an interpretation of a holy book, and the mistaken belief that blood in a carcass is in some way unclean.

Evidence from welfare assessment studies shows that: cutting the throat without prior stunning causes up to two minutes of extreme pain. Castration, disbudding, or beak-trimming, without anaesthetic or analgesic causes pain for many hours, and often leads to more prolonged pain because of neuroma formation. Tail removal prevents normal defence against flies in cattle and social signalling in pigs and dogs. Tail-biting by pigs and injurious behaviour by hens can be prevented by giving the animals manipulable materials and more space. This costs more but the painful procedures can be avoided. Foie-gras production necessitates confined rearing conditions, aversive force-feeding and failure of the detoxifying function of the liver so that death would result soon after the normal killing time. Caponising is a major operation that is painful and the wounds take some days to cease to cause pain. In all these cases, the main beneficiary is human and the cost is borne by the animal.

1. Introduction

Legislation and philosophical arguments about how animals should be treated refer to the welfare of the animals. The welfare of an animal is its state as regards its attempts to cope with its environment (Broom 1986). Well-being has the same meaning as welfare but welfare is considered more precise so is more often used in scientific and legal documents. Welfare is a characteristic of an animal at a particular time and should be translated into French as bien-être, not as bien-traitance which, like animal protection or good husbandry, is a human activity. The term “quality of life” means the same as welfare but is not normally used for brief periods of life, whereas we can consider the welfare of individuals over periods lasting for seconds, hours or years (Broom 2007). Welfare includes positive and negative feelings and the state of other mechanisms for coping and it can be assessed scientifically, for example by measuring behaviour, physiology, injuries or the functioning of systems for coping with disease (Fraser 2008, Broom 2014, 2016e, Broom and Fraser 2015). The evaluation of the strength of animal preferences is also important so that we can find out what conditions to use for animals in order to avoid poor welfare and maximise good welfare (Duncan 1992, Dawkins 2006, Kirkden et al. 2003).

Pain and fear are important aspects of suffering and poor welfare and measurement of these in farm animals has been the subject of the recent E.U. funded Animal Welfare Indicators (AWIN) project. There is clear scientific evidence for pain and fear systems in all vertebrate animals, including fish, and some invertebrate animals such as some molluscs – Cephalopoda (Octopus, Loligo, Sepia) and some crustaceans – Decapoda (Cancer, Homarus, Palaemon) (Elwood 2012, Broom 2013b, 2014, 2016b, Mather 2013, Sneddon et al., 2014). All of these are sentient (Duncan 2006, Broom 2014, 2016 a, c).

2. Pain assessment

Fig.1 Sheep with foot-rot which cannot stand comfortably on its hooves (photograph C. Rebelo)

How can we identify and assess pain? There has been recent AWIN work on sheep, horses and goats (McLennan et al. 2016). Indicators of pain during foot-rot, mastitis and pregnancy toxaemia were investigated. If a sheep is “standing” with its front feet bent under it so that it can avoid putting pressure on them (Fig. 1), the probability of pain in the feet is very high. This has long been known but it has recently been found that, when a sheep is in pain, it shows changes in facial expression that can be evaluated. Fig. 2 shows a normal sheep and Fig. 3 a sheep that is in pain. Many sheep with painful lesions show: orbital tightening, cheek tightening, ears turned down, and change in the shape of the mouth and nose. This is called a grimace and a very similar combination of movements is a pain indicator in humans. A scale of different intensities can be compiled and sheep showing this grimace had painful pathologies recognisable from other clinical signs (Corke et al. 2015, McLennan et al. 2016). The “grimace scale” can also be used for horses, mice, rabbits and other species (Keating et al., 2012, Defensor et al., 2012, Dalla Costa et al., 2014).

Fig. 2  Face of normal sheep (Photograph C. Rebelo)      
Fig.3  Face of sheep with foot-rot (Photograph C. Rebelo) 

There are many other behavioural and physiological indicators that can be used to quantify pain. For example, pain is also indicated by inflammation, as measured in sheep with foot-rot, by thermography and several blood chemicals. These various indicators of pain cease to be shown when the clinical condition disappears or when an effective anaesthetic or analgesic is used. As Flecknell et al. (2011) pointed out, the major challenge for pain research is being able to assess the emotional side of pain but the close correlation between the behavioural measures and the physiological changes strongly suggest that all of these measures indicate the negative pain feelings associated with pathology and tissue damage in these studies.

There are many indicators of good and poor welfare. Welfare indicators, like those described above, provide quantitative information about how much pain and other poor welfare is caused. However, the duration of the pain is important as well as its severity. When welfare is evaluated, the relationship between intensity and duration should be taken into account (Broom 2001), for example as shown in Fig. 4.

Fig.4 Examples of measures of severity of pain plotted against time (modified after Broom, 2001)

In Fig. 4, the area under the plot of severity against time is the magnitude of poor welfare. The maximum severity is the same in each example but the magnitude of poor welfare is much greater during procedure (a) than during procedure (b)

If an effect, like that shown in Fig. 4, is a benefit, the intensity of positive effects is measured and the magnitude of good welfare determined.

3. Examples of legally accepted pain or other poor welfare

In general, our laws prohibit treatment of animals that causes pain or other poor welfare (Broom, 2017). However, there are exceptions to these laws that permit pain or other poor welfare to be caused to animals. The following list shows some reasons for exceptions to laws intended to prevent poor welfare: