Why should environmental enrichment be used to improve welfare on mink farms

The aim of this review paper is to present a general scientific and political argument for the greater enrichment of mink cages. I first give an overview of the animal welfare issues common to many husbandry systems, before assessing how mink farming compares with other sectors. I highlight two ways in which mink farming (like many other forms of farming) could be improved in welfare terms: in its use of restrictive feeding, and the barren, unenriched nature of many animals’ cages (common in some countries, though now rare in others). I will also review in more detail what we know – both scientifically and practically – about specific possible enrichments for farmed mink. Even simple enrichments like wire cylinders, year-round straw, and lengths of rope may have marked effect on mink behaviour and welfare, and, especially in a climate where fur-farming seems to be scrutinised more closely and harshly than many other animal sectors, finding functional, cost-effective ways of enriching environments and reducing abnormal repetitive behaviours are to be encouraged. Introduction In this paper I first give a brief overview of the animal welfare issues common to many husbandry systems, before assessing how mink farming compares. I highlight two ways in which mink farming (like many other forms of farming) could be improved in welfare terms: in its use of restrictive feeding, and the barren, unenriched nature of many animals’ cages. I review literature on other species to explain why this last is important in terms of both stress reduction and proper forebrain development, and then review the extent to which we see abnormal repetitive behaviour like stereotypic pacing on mink farms. In my plenary talk itself, and also a subsequent companion paper (Mason in prep.), I will additionally review in more detail what we know – both scientifically and practically – about specific possible enrichments for farmed mink. The aim of this present review is to present a more general scientific and political argument for the greater enrichment of minks’ cages. Welfare issues in captive animals: on a spectrum from ‘good’ to ‘bad’, where does fur farming sit? Animal welfare relates to an animal’s affective (colloquially, ‘emotional’) state: what it feels. Good welfare thus means experiencing positive emotional states and negligible suffering, while poor welfare entails experiencing severe or prolonged states of suffering (e.g., Dawkins 1980, 1990; Mason & Mendl, 1993). Worldwide, more than 22 billion individuals are currently kept by humans for food, for research, for companionship, and in zoos (cf. the few million farmed mink). For these animals, being housed very differently from how they would live if free or wild, is nearly ubiquitous. Although the aims and methods of these various husbandry systems differ, common welfare themes therefore recur. Veterinary expertise, scientific research and common sense all show, for example, that hygiene, vaccination regimes, nutrition, handling regimes, stress and genotype IX International Scientific Congress in Fur Animal Production — Halifax, Nova Scotia, Canada, August 19-23, 2008 have major effects on physical health – with animals that are in pain, nauseous, or otherwise in discomfort from disease or injury obviously having poor welfare. Being unable to maintain homeostasis, due to insufficient access to food, water or a suitable thermal environment, causes both psychological stress and welfare problems from impaired physiological functioning. Housing conditions which restrict movement and/or present little opportunity for naturalistic behaviours, are typically non-preferred by animals, induce stress, and cause the development of abnormal repetitive activities like stereotypic pacing and furor featherplucking (all behaviours which I discuss in more detail below). Housing animals in groups, be they mothers with their offspring, or unrelated similar-age conspecifics, may help solve this problem, but often brings with it others: particularly competition for food, and aggression that subordinate animals cannot escape from. Finally, handling, transport and slaughter are often stressful processes for animals. These welfare issues occur and recur in many systems from the familiar to the exotic: laboratory mouse breeding units, poultry farms, pig farms, even timber camps using working elephants – and a myriad others. These recurring welfare concerns have therefore prompted the ‘Five Freedoms’ (Brambell, 1965) to become generally accepted tenets for ensuring good welfare, across a host of diverse systems; these are: (1) freedom from injury and disease; (2) freedom from hunger, thirst and malnutrition; (3) freedom from fear; (4) freedom from thermal or physical distress; and (5) freedom to express most ‘normal’ behaviors. These recurring welfare concerns also allow the exchange of ideas, opinions, techniques, data and welfare evaluations between scientists working on similar problems, even when the species and system they are studying varies. Such exchanges would suggest that in many ways, a well-run mink farm compares extremely favourably with many other animal industries -particularly with those in food animal agriculture (cf. Spruijt, 1999; also SCAHAW 2001 and Pedersen et al., 2002; Hansen 2007), but arguably also with many research animal facilities, and even some (the most environmentally restrictive) forms of petand zoo animal housing. For example, infant mink are left with their mothers until they have transitioned to solid food (unlike piglets and calves, for instance); left physically intact (not castrated, branded, tail-clipped, tooth-clipped or given any other type of painful mutilation, unlike e.g. piglets, calves, lambs, laying hens, and many research rodents); and often housed with siblings beyond that. Overall kit mortality to weaning age has been estimated at between 20 and 35% (reviewed SCAHAW 2001); fairly similar to that seen in piglets without farrowing crates (reviewed Mellor & Stafford 2004), and lower than rates seen in some bear and ‘big cat’ species in zoos (Clubb & Mason, 2003, 2007). Levels of fear are typically low. Mink cages give animals space to move, separate resting/nesting areas, and separation from their faeces (unlike typical poultry, pig and some dairy systems). Stereotypic behavior on mink farms is less prevalent than in say, tethered dry sows, isolated laboratory macaques, or even zoo-housed giraffes (surveyed in Mason & Latham, 2004; Mason et al., 2007), and when mink are well-fed, it is also less time-consuming than that performed by many carnivore species in zoos (Clubb & Mason, 2003, 2007). Adult mink mortality rates are on average 2-5% per year (reviewed SCAHAW 2001); this contrasts with, say the 16-17% first and second litter sows that are culled for lameness (e.g. Gill, 2007; to give just one example; data from intensive dairy cattle or aviary laying hens would provide poorer contrasts still). Finally, mink are hardly ever transported (unlike the vast majority of food animals); and euthanasia is on-farm, and typically an extremely swift process.