Project Abstract

Numerous studies conducted to assess welfare of domestic dogs housed in kennel facilities have reported that these dogs experience suboptimal living conditions. One important goal of improving welfare of kennelled dogs is to reduce their stress levels, and one recommended approach for improving welfare of kennelled dogs is group or social housing. The beneficial effects of management changes designed to achieve this goal should be measurable in individual animals. Stress is evident through behaviours exhibited, as well as via the concentration of cortisol, a key hormone reflecting stress. Using behavioural and hair cortisol measures, we conducted a pilot study to measure the impact of switching dogs housed in a long-term kennels facility from solitary to pair housing, using both within-subjects and between-groups comparisons. Considerable individual variation in dog responses was noted, with only two of eight pair-housed dogs showing significant declines in multiple stress-related behaviours once in pair housing. The most sensitive behaviours were active vigilance and repetitive movements (such as jumping and pacing). Barking was reduced overall in the facility following the housing change, even among dogs still in solitary housing. The long-term stress as reflected in hormone deposition in hair also provided encouraging indications that the dogs experienced lower stress levels when in paired housing; dogs showed a significant decline in hair cortisol levels from the first (prehousing change) to second (postintervention) samples. Domestic dogs are social animals, and numerous indications of potential benefit were recorded with no negative impacts seen. Based on our findings, we recommend pair or group housing of compatible dogs as a promising addition to the strategies available to those seeking to improve welfare of kennelled dogs. Future studies using higher numbers of animals and that include tracking of hair cortisol, vigilance behaviour, repetitive movements and barking would be desirable.

Project Overview

It is well documented that captive animals experience stress (eg, Beerda and others 2000, Markowitz and Woodworth 1978, Morris and others 2011), and a goal of optimal welfare should be to minimise stress. As we work towards this goal by changing the social or physical environment, the effect of the change should be reflected by the animal; it is important therefore to establish meaningful, measurable outcomes of any inputs designed to increase welfare (Maple and Perdue 2013). Stress is evident through behaviours, as well as via the concentration of the main stress hormone, cortisol. Numerous studies conducted to assess welfare of domestic dogs (Canis familiaris) housed in kennel facilities have reported that dogs housed in kennels (particularly for longer periods of time) experience suboptimal living conditions (eg, Hubrecht and others 1992, Beerda and others 1999, 2000, Stephen and Ledger 2005). Studies of kennelled dogs have used behavioural, physical, physiological and (more recently) cognitive measures of welfare (see Hewson and others (2007) for a review; also Titulaer and others (2013) for more recent work). Welfare of these dogs may be compromised due to numerous factors: lack of exercise and/or control over their environment, confinement to a small area, minimal social contact (Hetts and others 1992, Hennessy 2013, Rooney and others 2009), novelty of the environment (Tuber and others 1996, Tuber and others 1996), high and/or unpredictable noise levels and disrupted routines (Beerda and others 1997, Hennessy 2013, Hubrecht and others 1992). Activation of the hypothalamic-pituitary-adrenal (HPA) axis indicates that dogs experience acute stress following admission to kennels, and some experience chronic stress when kennelled long term (Beerda and others 2000, Rooney and others 2007). Acute stress has been measured using cortisol levels (the end product of the HPA axis) in serum, saliva, urine (specifically as the cortisol/creatinine ratio) and faeces (eg, Beerda and others 2000, Titulaer and others 2013, Hennessy 2013, Part and others 2014).
Chronic stress levels in dogs have more recently been assessed using cortisol in hair samples (Bryan and others 2013, Siniscalchi and others 2013, Roth and others 2016). Salivary and faecal cortisol measures provide information about stress experienced in the preceding minutes (saliva) or hours (faeces). Therefore, to monitor chronic stress from less desirable social or physical environments using faeces or saliva, a higher number of samples must be collected at multiple time periods. Hair integrates cortisol and other steroids over the entire period of hair growth, thus representing stress and reproductive activity over the preceding weeks to months (Sheriff and others 2011, Bryan and others 2013). Measurement of cortisol immunoreactivity in hair is therefore both practical and meaningful, as it is less invasive than serum and salivary cortisol measurements (Bennett and Hayssen 2010), more indicative of long-term or chronic stressors than are cortisol in serum, faeces or saliva, and less labour-intensive than repeated salivary or faecal measurements (Russell and others 2012). Further, because of the impact on diurnal rhythm of cortisol release in the body on acute stress measures (such as salivary and serum sampling), cortisol as measured in hair is the most meaningful measure of chronic stress in animals (Bryan and others 2013). Hair cortisol analysis has been used, for example, to assess stress associated with a major housing change in rhesus macaques (Davenport and others 2006). In addition, cortisol levels in hair are less variable between individuals than cortisol in saliva, faeces, etc (Bennett and Hayssen 2010, Bryan and others 2013). Bennett and Hayssen (2010) reported positive correlations between hair and salivary cortisol samples, although this finding was not supported by Bryan and others (2013). Importantly for the value of this new methodology, Bennett and Hayssen (2010) reported no significant effects of age, breed, weight or neuter status on hair cortisol, which supports hair cortisol as a useful tool for comparisons of individual traits such as resilience to chronic stress.
Numerous authors have noted that dogs vary in their individual responses to stress, behaviourally and physiologically (eg, Hiby and others 2006, Bennett and Hayssen 2010, Titulaer and others 2013, Part and others 2014). However, it is generally agreed that maladaptive and repetitive behaviours such as self-mutilation and stereotypies (defined as ‘repetitive, invariant behaviour patterns with no obvious goal or function’; Mason 1991) are indicative of chronic stress (Beerda and others 2000, Hewson and others 2007). In addition to physiological changes (eg, in cortisol levels), other changes commonly associated with chronic stress of kennel life include indications of frustration (such as chewing, vocalising), conflict (body-shaking, paw-lifting), coprophagy (Beerda and others 1997) and a lowered/fearful posture (Hewson and others 2007). Other behavioural changes, such as increased or decreased activity levels, vary by dog and by study (eg, Hubrecht and others 1992, Hetts and others 1992, Beerda and others 2000). Most studies report increased activity in dogs living in suboptimal housing conditions, likely associated with repetitive behaviours; reports of reduced activity in dogs living in suboptimal conditions may reflect fatigue or boredom (as suggested by Beerda and others 1997) or learned helplessness. Apparent over-reaction by kennelled dogs to relatively mild stimuli, often triggering repetitive behaviours such as circling and jumping, has also been documented (Beerda and others 2000, Hewson and others 2007), perhaps due to the dog’s frustration at not being able to reach and interact with the stimulus. Chronic stress has negative impacts on the overall health and wellbeing of kennelled dogs (Hennessy 2013). Because of individual variation among dogs, facilities and methods used to assess responses to interventions designed to improve welfare of kennelled dogs, many authors have suggested using multiple measurements (ie, physiological and behavioural) and an integrated analytical approach (Beerda and others 2000, Hiby and others 2006, Titulaer and others 2013).
One frequently cited concern about welfare of dogs living in kennelling facilities is solitary housing. Although kennel size is an often-cited concern, Hetts and others (1992)note that social isolation may be equally or more harmful than spatial restriction. Group housing is a suitable alternative from a welfare perspective, providing opportunities for positive interaction with other animals including play, companionship, physical connection and socialisation. Mertens and Unshelm (1996) report in a study of 211 shelter dogs that a high percentage of dogs housed alone suffered from behavioural problems (31 per cent), with 10 per cent developing stereotypies. They also found that increased aggression in group-housed dogs, a frequently cited reason to house dogs singly, was not seen in their study. Ninety-one per cent of social confrontations between dogs in the Mertens and Unshelm (1996) study were settled without actual physical conflicts. Hubrecht and others (1992) also noted that dogs differed greatly in their behaviour when housed singly versus in groups: dogs housed alone were more inactive (72-85 percent of time v 54-62 per cent in group-housed dogs) and spent more time in non-social repetitive behaviours like circling (4-5 per cent of time compared with 0.9-2 per cent in group-housed dogs). Group housing can be used to provide a more enriched and varied environment (ASV 2010), and providing dogs with increased social contacts may enable a dog to gain more control over his/her environment. Actual or even perceived control over one’s environment is an important aspect of quality of life, which may in turn increase the dogs’ ability to cope with the pressures of confinement (Hubrecht and others 1992). The Center for Shelter Dogs (Tufts University Cummings School of Veterinary Medicine, Medford, Massachusetts, USA) states that ‘co-housing dogs must be a consideration for dogs kept longer than two weeks’ (Center for Shelter Dogs online, accessed June 2015). There is no single accepted definition of what constitutes ‘long-term housing’ for kennelled dogs, with studies reporting increased occurrence of chronic stress-related behavioural issues in as little as 4-8 weeks following admission to a kennels facility (eg, Beerda and others 1999, Stephen and Ledger 2005). For this study, we consider ‘long-term’ to be any stay longer than six months.
In the present study, our goal was to assess the impact of switching dogs housed in a long-term kennel facility from solitary to compatible pair housing, using multiple measures (behavioural and hair cortisol), and considering within-subjects and between-subjects comparisons. Due to logistical constraints, we consider this a pilot study that can provide baseline information for future work. Our hypotheses were that (1) there would be a measurable reduction in physiological and behavioural stress indicators in dogs housed in compatible pairs, relative to dogs in the same facility remaining in solitary housing for the same time period; and (2) hair cortisol results would reflect beneficial effects similar to those reported in earlier studies of group housing of kennelled dogs.
Materials and methods
Study population
The colony ranges in size between 20 and 30 dogs; size of individual dogs varies but most are of medium build (15-20 kg). Dogs are accepted as donations to the programme as needed for teaching purposes. Most dogs in the colony were found as strays, or surrendered by local owners who could no longer care for them. All dogs are behaviourally assessed prior to acceptance into the colony, and dogs displaying aggressive tendencies during assessment or during the two-week to three-week quarantine period are not added to the colony. Dogs in the colony are individually housed in kennels for up to 24 months prior to adoption into suitable homes. Individual kennels are 2.36 m long, 1.07 m wide and 2.24 m high, with grates on both sides and the door allowing visual contact and limited (non-contact) interaction with neighbouring dogs and passing dogs, kennel staff and students (fig 1). Dogs are fed once per day and walked outdoors twice per day (for 15-30 minutes per walk), and kennels are cleaned once per day; these activities are done at consistent times each day. There is an active enrichment programme whereby dogs are taken out regularly (a minimum of two times per week) for training and/or socialising with conspecifics or human companions, in addition to their duties in scheduled teaching labs (one to three labs per week). Nonetheless, while in the kennels some of these dogs develop stereotypies indicative of chronic stress (Grigg and Piehler 2015). The facility management agreed to the conversion of four sets of kennels into shared housing, which would allow eight dogs to be placed in pair housing. Twelve healthy mixed-breed dogs, ranging in age between 1.8 and 4 years, and who had been residing in the colony for a minimum of six months (range: 8-20 months; mean ± se: 12.2±1.13 months) were included in the study. From these 12, eight dogs were randomly selected for pair housing; the remaining four dogs were left in solitary housing throughout the study. Seven (58 per cent) of the dogs were female, five (42 per cent) were male and eight of the 12 (67 per cent) were neutered at the time of the study (table 1). This resulted in an imbalance in the ratios of intact:altered dogs between our treatment versus control groups. However, given the lack of significant effect of age or neuter status on hair cortisol (Bennett and Hayssen 2010), and the fact that all dogs entering the kennels facility had passed an initial behavioural assessment (ruling out dogs with elevated levels of aggression), we felt that this imbalance would not represent a significant confounding variable in these comparisons.
ata collection (behavioural)
All 12 dogs were videotaped in their solitary kennels for 30 minutes, twice per week at the same time each day, for two weeks prior to the transition of eight of the dogs to pair housing (and prior to the possible confounding stressors of construction work to convert the existing single kennels to shared/pair kennels). Timing of video recording was selected to avoid predictable disruptions to the dogs’ daily routine, such as student walking, feeding and kennel cleaning, and video data for this pilot study was collected at consistent times each day in order to minimise any additional variation in behaviours associated with time of day. GoPro Hero3 (GoPro, San Mateo, California, USA) cameras were set up on the kennel opposite the focal (subject) dog’s kennel, after which the researcher left the area to avoid influencing the dog’s behaviour. Following baseline data collection, eight individual kennels were converted into four shared/pair kennels, by installing a guillotine-style door in the concrete wall between two adjacent kennels, and allowing dogs to interact freely with each other during daylight hours. This design had the benefit of maintaining the same average kennel space per dog, to reduce any confounding effects of an increase in kennel space on behaviour and cortisol. The dogs were separated and the guillotine door closed during their once-daily feeding and at night when no kennel staff were on site. Following completion of the conversion construction and a one-week ‘rest’ period postconstruction, eight dogs (hereafter ‘experimental dogs’) were moved into their new shared housing, and video data collection was resumed for eight weeks on all 12 dogs (eight now in shared housing, four remaining in solitary housing). The four dogs that remained in solitary housing (‘control dogs’) were used as environmental controls, providing information on behavioural effects of any ambient changes distinct from shared housing, which could have confounded the interpretation of results.
From the video footage, we recorded occurrence and duration of the following behaviours, based on the literature on behaviours indicative of stress in kennelled dogs: repetitive vocalisation (barking), circling, spinning, pacing, barrier jumping and conflict-related behaviours, as well as time spent resting (lying down and/or sleeping). To allow for the dogs to adjust to the researcher leaving the kennels area, we began data recording after 1 minute of video had passed. Footage when the dogs were out of view was removed from the analysis. We used focal animal sampling (Altmann 1974) and recorded behaviour in two ways: continuous (in which start and end times of all behaviours were recorded and considered ‘duration’ of behaviours) and instantaneous scan sampling (in which behaviour and body posture of the focal dog were recorded at 1-minute intervals). For continuous sampling, the following behaviours were recorded: barking, jumping, pacing (repetitive movement around kennel), resting/sleeping, spinning (ie, repetitive, tight circles), vigilance (when dog was alert and actively looking at something outside his/her kennel) or ‘other’ (with specific behaviour noted). For instantaneous sampling, the following variables were recorded at each 1-minute scan: body posture (sitting, standing or lying down); whether or not the dog was actively vigilant or barking; movement type (none, jumping, pacing, spinning or directional movement from one part of the kennel to another); and any social behaviour. Examples of social behaviour for cohoused dogs consisted of none, in physical contact with, playing with or exhibiting aggression towards another dog in a directly adjacent kennel or in the shared kennel. Examples for solitary dogs consisted of none, any affiliative or any aggressive interaction with a dog in a directly adjacent kennel 
Data collection (hair cortisol)
A 10 cm × 10 cm patch of hair was collected from the shoulder of all dogs using hand-held electric clippers with a number 10 blade, at two times: prior to the start of the kennels construction work (for baseline cortisol levels) and after the dogs had been in the shared/pair housing for eight weeks (for postintervention levels). Three days after being moved into the pair housing, the patch was reshaved on all dogs, so that hair growth in the second sample reflected stress levels during the treatment period (when the paired dogs were cohoused).
Sample analysis (hair cortisol)
We used a commercial enzyme immunoassay kit (Salimetrics, Philadelphia, Pennsylvania, USA), previously validated in our laboratory (Bryan and others 2013), to quantify cortisol in hair as described below. Hair samples were processed as described in Bryan and others (2013) with the following modifications. After distilled water and isopropanol washes, the dried hair samples were powdered in a ball mill (Mixer Mill 200, Retsch, Haan, Germany), then 20 mg was weighed into a 20 ml glass scintillation vial. High Performance Liquid Chromatography (HPLC)-grade methanol, 2.5 ml, was added to each vial. Samples were sonicated, extracted and centrifuged for 15 minutes at 14 000 g. A 0.31 ml aliquot was removed and dried under a gentle stream of nitrogen. Samples were reconstituted in 720 µl of 5 per cent methanol followed by 95 per cent assay diluent. Each sample, in duplicate, was assayed according to kit instructions.
References
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