The effects of enriching laboratory cages using various physical structures on multiple measures of welfare in singly-housed rats

The single housing of laboratory rats may be recommended in some situations such as hypothesis-driven or test-specific studies, during electroencephalogram recording of phases of sleep and after surgical procedures. However, as single housing of laboratory rats has been shown to be stressful, modification of the housing environment is needed to improve the welfare of these animals. This experiment was carried out to investigate the long-term effects of environmental enrichment on some behavioural, physiological, pathological and psychological measures of welfare. With two batches of animals, 24 rats were housed singly in either enriched cages (EC) (n = 12 cages) or unenriched cages (UC) (n = 12 cages). Behaviour was sampled every week and so was body weight and weight gain over a six-week observation period. Behaviours of the rats in the elevated plus-maze were recorded on the seventh week, whereas organ weights were recorded postmortem. The results revealed that long-term single housing of rats in super-enriched cages increased levels of indicators of good welfare including sleep, exploration, movement and feeding behaviour, body weights, weight gains and the relative weights of the thymus gland and spleen, and decreased levels of indicators of poor welfare such as stationary behaviour and the relative weight of adrenal glands. Thus, enrichment of conventional cages of newly weaned singly-housed laboratory rats with multiple physical structures appeared to improve their ability to control the environment and to promote their species-specific behaviour; changes that can ultimately result in good welfare.     

Part-time grouping of rabbit does in enriched housing: effects on performances,injury occurrence and enrichment use

Collective housing is perceived as a possible way to improve rabbit welfare, especially among adult females, which are normally individually housed. Part-time group housing seems to allow a better balance between welfare and health than continuous group housing, but practical implementation and consequences for reproductive performance have not been extensively studied. The aim of this work was to compare weight, feed intake, litter size, injury occurrence, body integrity, and spatial location of female rabbits housed part-time in group housing (PGH group, n = 32) or housed individually (IH group, n = 8). Females were grouped by opening connecting hatches between four individual enriched cages (platform, wood stick and gnawing block). Collective housing started 12 days after artificial insemination and was interrupted at the 10th day (instead of the 15th day later as originally planned) due to high injury rates and severe injuries caused by fighting. The proportion of injured females increased from 25% on the first day of grouping to 63% on the 10th day. Female weight gain during the experiment was similar in the two groups. Litter size at weaning was 9% lower in the PGH group than in the IH group (9.2 vs 10.0, P < 0.01). Platform use was recorded in 32% of the observations and was the highest during the 2 weeks before weaning (46% and 47% of total observations, P < 0.05). During the grouping period, there were at least two females in the same housing unit in 59.4% of the cases, at least two females were located on the same level in 31.3% of the cases. In conclusion, connecting individual cages is an ergonomic solution for part-time group housing, but does not prevent fights for the establishment of a social hierarchy. This is detrimental to the health and body integrity of female rabbits.     

Reproductive performance of rhesus macaques (Macaca mulatta) in two outdoor housing conditions

This study examined the reproductive performance of rhesus macaques maintained in two different housing conditions: high-density semi-sheltered gang cages and low-density outdoor corrals. Two hundred sixteen subjects were housed in 49 gang cages, each of which contained one breeding male and between one and eight breeding females. Two hundred seven subjects were housed in 13 corrals, each of which contained between two and four breeding males and between 9 and 26 breeding females. Over a 3-year period, pregnancy, live birth, and production rates were significantly greater for females in corrals than for females in gang cages. Fetal death rate was lower in corrals than in gang cages, while neonatal death rates did not differ between housing conditions. These differences did not result from potential confounds such as differential age structures or virological statuses between housing conditions. We conclude that, for rhesus macaques, outdoor corral housing leads to better reproductive performance than does semi-sheltered gang housing, probably as a result of increased individual space and relaxation of intense social stressors.     

Welfare, health, and hygiene of laying hens housed in furnished cages and in alternative housing systems

The aim of this review was to compare welfare, health, and hygienic status of laying hens housed in furnished cages and in alternative systems. In alternative systems (floor housing and aviaries), birds have more freedom of movement and a more complex environment than in furnished cages. However, housing birds in much larger flocks in alternative systems leads to an increased risk of feather-pecking. Furthermore, air quality can be poorer in alternative systems than in furnished cages. This can affect health and hygienic status. There are only limited data on a direct comparison between furnished cages and alternative systems. Therefore, there is a need for an on-farm comparison of welfare, health, and hygienic status in these systems.     

Benefits of a Ball and Chain: Simple Environmental Enrichments Improve Welfare and Reproductive Success in Farmed American Mink (Neovison vison)

Can simple enrichments enhance caged mink welfare? Pilot data from 756 sub-adults spanning three colour-types (strains) identified potentially practical enrichments, and suggested beneficial effects on temperament and fur-chewing. Our main experiment started with 2032 Black mink on three farms: from each of 508 families, one juvenile male-female pair was enriched (E) with two balls and a hanging plastic chain or length of hose, while a second pair was left as a non-enriched (NE) control. At 8 months, more than half the subjects were killed for pelts, and 302 new females were recruited (half enriched: ‘late E’). Several signs of improved welfare or productivity emerged. Access to enrichment increased play in juveniles. E mink were calmer (less aggressive in temperament tests; quieter when handled; less fearful, if male), and less likely to fur-chew, although other stereotypic behaviours were not reduced. On one farm, E females had lower cortisol (inferred from faecal metabolites). E males tended to copulate for longer. E females also weaned more offspring: about 10% more juveniles per E female, primarily caused by reduced rates of barrenness (‘late E’ females also giving birth to bigger litters on one farm), effects that our data cautiously suggest were partly mediated by reduced inactivity and changes in temperament. Pelt quality seemed unaffected, but E animals had cleaner cages. In a subsidiary side-study using 368 mink of a second colour-type (‘Demis’), similar temperament effects emerged, and while E did not reduce fur-chewing or improve reproductive success in this colour-type, E animals were judged to have better pelts. Overall, simple enrichments were thus beneficial. These findings should encourage welfare improvements on fur farms (which house 60-70 million mink p.a.) and in breeding centres where endangered mustelids (e.g. black-footed ferrets) often reproduce poorly. They should also stimulate future research into more effective practical enrichments.     

Increased survival and reproductive success associated with stereotypical behaviours in laboratory-bred bank voles (Clethrionomys glareolus)

The aim of this study was to examine whether voles performing stereotypic behaviours (Ster) differed in physical welfare from voles, which did not develop stereotypies (N-Ster). The chosen variables were reproductive success and capacity to survive barren housing conditions. Furthermore, effect of weight on proneness to develop stereotypic behaviours were examined. Singly housed Ster (n = 62) in barren cages showed superior survival when compared to similar housed N-Ster (n = 38; p = 0.002). Furthermore, Ster females (n = 25) gave birth to both a first and second litter faster than N-Ster females (n = 14; p ≤ 0.019). Litter size, number of weanlings and proportion of barren females did not differ between Ster and N-Ster, but pups from Ster experienced a higher pre-weaning mortality in the second litter (p = 0.0095). Voles classed as Ster within age 6 month (n = 55) weighed less than same aged N-Ster (n = 45) already from weaning (21 days; p = 0.0204). However, weight at weaning, whether LIGHT (weight ≤ median; n = 47) or HEAVY (weight > median; n = 53), had no effect on subsequent development of stereotypies in terms of either onset age or fraction which developed stereotypies. The results suggested that Ster had better physical welfare, as reflected in better survival, than N-Ster when housed singly and a higher reproductive success when used as breeders.     

Does Rearing Laying Hens in Aviaries Adversely Affect Long-Term Welfare following Transfer to Furnished Cages?

This study tests the hypothesis that hens that are reared in aviaries but produce in furnished cages experience poorer welfare in production than hens reared in caged systems. This hypothesis is based on the suggestion that the spatial restriction associated with the transfer from aviaries to cages results in frustration or stress for the aviary reared birds. To assess the difference in welfare between aviary and cage reared hens in production, non-beak trimmed white leghorn birds from both rearing backgrounds were filmed at a commercial farm that used furnished cage housing. The videos were taken at 19 and 21 weeks of age, following the birds'' transition to the production environment at 16 weeks. Videos were analysed in terms of the performance of aversion-related behaviour in undisturbed birds, comfort behaviour in undisturbed birds, and alert behaviour directed to a novel object in the home cage. A decrease in the performance of the former behaviour and increase in the performance of the latter two behaviours indicates improved welfare. The results showed that aviary reared birds performed more alert behaviour near to the object than did cage reared birds at 19 but not at 21 weeks of age (P = 0.03). Blood glucose concentrations did not differ between the treatments (P>0.10). There was a significant difference in mortality between treatments (P = 0.000), with more death in aviary reared birds (5.52%) compared to cage birds (2.48%). The higher mortality of aviary-reared birds indicates a negative effect of aviary rearing on bird welfare, whereas the higher duration of alert behavior suggests a positive effect of aviary rearing.     

The effect of cage size and enrichment on core temperature and febrile response of the golden hamster

The aim of this study is to determine the effect of cage size and cage enrichment. Golden hamsters were individually housed in standard cages of four different sizes and in enriched cages of three different sizes since 3 weeks of age. Each of the seven housing groups consisted of 12 hamsters. After 14 weeks of housing in their respective environments the measurements started. The mean baseline rectal temperature was significantly higher in hamsters housed in small cages than in hamsters housed in large cages. After the injection of fever-inducing lipopolysaccharide rectal temperature increased by 1 to 2 degrees C. The increase of rectal temperature and the fever index were the highest in animals housed in large cages and the smallest in animals housed in small cages. Through cage enrichment and increasing cage size the mean febrile response increased while the mean baseline rectal temperature decreased. Cage size and cage enrichment had no effect on the dispersion of the measured values. The differences in microclimate between large and small cages were too small to have an effect on thermoregulation. The results indicate that housing in small cages induce chronic stress which obviously affects thermoregulation. The findings demonstrate that the results of some physiological experiments are significantly influenced by the pre-experimental housing conditions.     

Effects of cage density on behavior in young adult mice

Optimal housing conditions for mice can be achieved by minimizing environmental variables, such as those that may contribute to anxiety-like behavior. This study evaluated the effects of cage size on juvenile mice through assessment of differences in weaning weight, locomotor skills, and anxiety-like behavior. Eighteen pairs of male and pregnant female Swiss-Webster (Cr:SW) mice were housed in 3 different caging scenarios, providing 429, 505, or 729 cm2 of space. Litters were standardized to 10 pups per litter in each cage. Mice reared in each caging scenario were assessed with the open-field, light-dark exploration, and elevated plus-maze tests. No differences in weaning weight were noted. Mice reared in the 505- and 729-cm2 cages explored a significantly larger area of the open-field arena than did those in the 429-cm2 cages. Those reared in the 505-cm2 cages spent more time in the center of the open field than did those in the 729-cm2 cages, suggesting that anxiety-like behavior may be increased in the animals housed in the larger cages. This study did not establish a consistent link between decreased floor space and increased anxiety-like behavior; neither does there appear to be a consistent effect of available floor area on the development of locomotor skills on mouse pups.     

The effect of housing and environmental enrichment on stereotyped behavior of adult vervet monkeys (Chlorocebus aethiops)

Little information is available on the response of vervet monkeys to different housing conditions or on the suitability of enrichment devices or methods for vervet monkeys. In this study, the authors evaluated the occurrence of stereotyped behavior in adult vervet monkeys under various conditions of housing and enrichment. The variables included cage size, cage level (upper or lower), enrichment with a foraging log, enrichment with an exercise cage and presence of a mate. The authors first determined the incidence of stereotyped behavior in captive-bred, singly housed adult female and male vervet monkeys. They then exposed monkeys to different housing and enrichment situations and compared the incidence of stereotyped behavior among the monkeys. The authors found that more females than males engaged in stereotyped behavior and that females, on average, engaged in such behavior for longer periods of time than males. Stereotyped behavior was most often associated with a small, single cage. The average amount of observed stereotyped activity in monkeys housed in a small cage was significantly lower when the monkeys had access to either a foraging log or an exercise cage. Stereotyped behavior was also lower in female monkeys that were housed (either with a male or without a male) in a larger cage. The least amount of abnormal behavior was associated with the largest, most complex and enriched housing situation. Males and females housed in cages on the lower level of two-level housing engaged in more stereotyped behavior than did monkeys housed in the upper level, regardless of the presence or type of enrichment provided.     

Motivation to dust-bathe of laying hens housed in cages and in aviaries

New housing systems for commercial egg production, furnished cages and non-cage systems, should improve the welfare of laying hens. In particular, thanks to the presence of a litter area, these new housing systems are thought to satisfy the dust-bathing motivation of hens more than in conventional cages, in which no litter area is present. However, although apparently obvious, there is no concrete evidence that non-cage systems, particularly aviaries, satisfy hens' motivation to dust-bathe and thus improve hens' welfare in terms of dust-bathing behaviour. The aim of this study was to compare hens' dust-bathing motivation when housed for a long time under similar conditions to commercial conditions in laying aviaries (with litter) and in conventional cages (without litter). Three treatments were compared: hens reared in floor pens then housed in conventional cages, hens reared in furnished floor pens then housed in a laying aviary, and hens reared in rearing aviaries then housed in a laying aviary. All three treatments provided access to litter during the rearing period. After transfer to the laying systems, access to litter was maintained for the aviary hens but stopped for the cage hens. Twelve groups of four hens per treatment were tested 36 to 43 weeks after transfer. The hens were placed in sawdust-filled testing arenas, and latency to dust-bathe, duration and number of dust baths, and number of hens dust-bathing were recorded. Latency to dust-bathe was shorter, dust baths were longer and more numerous and more hens dust-bathed among cage hens than among aviary hens. Our results indicate that hens' motivation to dust-bathe was more satisfied in laying aviaries than in conventional cages. Thus, laying aviaries improve hens' welfare in term of dust-bathing behaviour compared with conventional cages.     

Effect of castration on rabbits housed in littermate pairs

Conventional solitary caging for research rabbits precludes many postural and social behaviors. Several studies that have investigated enrichment strategies for rabbit does have found intact males usually too aggressive for paired or group housing. This study investigated the possibilities that male siblings will remain compatible if never separated from birth and that castration will improve compatibility among young sibling male rabbits. As a side benefit of pair housing for all rabbits, the larger cages (modified dog cages) allowed rest and other postures not possible in conventional single cages. In addition, there was no evidence of the stereotypies observed among individually housed rabbits. Castrated, post-weanling, male, Flemish Giant x Giant Chinchilla rabbit littermates demonstrated a significantly higher level of living together compatibly than did the intact controls. All rabbits chose to rest in close proximity or contact, although this preference was stronger in castrated males. During puberty, intact males displayed more serious aggression. We conclude that young adult littermate rabbits can live compatibly as pairs and that castration improves compatibility among males. Paired rabbits exhibit many postures and behaviors that are not possible in the small, solitary cages currently listed as minimum recommendations.     

The effects of enhancing cage complexity on the behaviour and welfare of laboratory rats

This experiment was carried out to investigate the long-term effects of enhancing cage complexity on behavioural measures of welfare in laboratory rats. We housed 72 rats in groups of four in either ‘enriched’ or ‘unenriched’ cages for six weeks. Scan and focal animal sampling were conducted in both the light and dark phase of the second, fourth and sixth weeks. Results revealed that rats in the ‘enriched’ cages showed longer durations of sleep behaviour, and low levels of agonistic behaviour compared to rats in the ‘unenriched’ cages. Results importantly demonstrated that the behavioural changes observed in the enriched environment were due to the presence of the enrichments themselves in the cages (indirect effects) and not due merely to rats interacting with the enrichment items in their environment. Thus, enhancing the complexity of conventional laboratory cages can promote behaviour such as longer bouts of sleep that is likely to be indicative of good welfare, and diminish levels of behaviour such as aggression that is likely to lead to poor welfare.     

Effects of early weaning and housing conditions on the development of stereotypies in farmed mink

Female mink pups were weaned at 6, 8 or 10 weeks of age and subjected to two different housing conditions. They were either kept together with a single male sibling in traditional mink cages (30x45x90 cm) or housed socially with all litter-mates in an alternative system consisting of three adjoining traditional cages (90x45x90 cm). All cages were supplied with nest boxes. At 5 months of age, the siblings were removed leaving the females socially isolated in the two different cage systems. Females' stereotypies were quantified by repeated scanning observations under the social housing conditions immediately before removal of the siblings, and again at the age of 7 and 9 months, when the animals had stayed solitary in the two systems for 2 and 4 months. Solitary females showed significantly more stereotypies than females under social housing conditions in both cage systems. Stereotypies were more frequent in the smaller traditional cages. Stereotypies declined from 7 to 9 months of age among solitary animals in traditional cages but not in alternative cages. Early-weaned solitary females in traditional cages showed more stereotypies than later-weaned animals, but only when measured at the age of 7 months. It is suggested that early weaning, individual housing and small cages promote the development of stereotypies in farmed mink. The influence of early weaning on stereotypies seems to decline with age, while effects related to individual housing and small cages appear to be more persistent.     

Response of adult New Zealand white rabbits to enrichment objects and paired housing.

Enhancing the psychological well-being of laboratory animals has received much attention recently. Although many studies have been undertaken to determine the effects of cage enrichment techniques on dogs and nonhuman primates, other than scant empirical observations, little has been done to measure these events objectively in lagomorphs. We studied adult female New Zealand White (NZW) rabbits to learn if, when given the opportunity, individual rabbits would use different enrichment objects placed in their cages, and to determine if rabbits preferred to be in proximity to one another, or apart. Three different objects were evaluated with eight rabbits individually housed in conventional cages. Each object introduced into individual rabbit cages stimulated substantial interaction, especially chewing behavior. Eight other rabbits were pair-housed in a modified caging system with a special access port between two separate cages. When given a choice, rabbits preferred to be in the same cage with other rabbits. In both studies, individual behaviors were monitored, as well as either the type of interaction and percentage of observations spent with each object or, in the housing study, percentage of observations involved with different types of activity, and relative location of the paired rabbits.     

Influence of housing conditions on pregnancy outcome in cynomolgus monkeys (Macaca fascicularis)

Female cynomolgus monkeys (Macaca fascicularis) were kept under 3 different housing conditions: individually in type A cages (45 X 45 X 60 cm), individually in type B cages (70 X 70 X 100 cm) and as couples in type B cages. Primigravida did not show early embryonic mortality, differing significantly from 11.5% early losses in multigravida. Early embryonic mortality was not affected by housing condition. Further reproductive failure rates did not differ significantly for primigravid (18.5%) and multigravid females (24.0%), though abortion tended to occur more frequently in primigravida. Perinatal mortality (16.1%) accounted for most of the losses under each housing condition. More successful pregnancies (90%) were recorded for females housed individually in type B cages than for females housed in type A cages (68%). About 50% of the couples originally established remained until weaning of their infants, yielding 77% viable offspring. For multigravid females statistical evaluation showed a significant effect of housing conditions on reproductive outcome (X2-test 0.01 less than P less than 0.05) that could be entirely attributed to low losses in females housed individually in type B cages. It is concluded that housing conditions can have a profound influence on reproductive success in cynomolgus monkeys.     

Response,use and habituation to a mouse house in C57BL/6J and BALB/c mice

Animal welfare depends on the possibility to express species-specific behaviours and can be strongly compromised in socially and environmentally deprived conditions. Nesting materials and refuges are very important resources to express these behaviours and should be considered as housing supplementation items. We evaluated the effects of one item of housing supplementation in standard settings in laboratory mice. C57BL/6JOlaHsd (B6) and BALB/cOlaHsd (BALB) young male and female mice, upon arrival, were housed in groups of four in standard laboratory cages and after 10 days of acclimatization, a red transparent plastic triangular-shaped Mouse House™ was introduced into half of the home cages. Animals with or without a mouse house were observed in various contexts for more than one month. Body weight gain and food intake, home cage behaviours, emotionality and response to standard cage changing procedures were evaluated. The presence of a mouse house in the home cage did not interfere with main developmental and behavioural parameters or emotionality of BALB and B6 male and female mice compared with controls. Both strains habituated to the mouse house in about a week, but made use of it differently, with BALB mice using the house more than the B6 strain. Our results suggest that mice habituated to the mouse house rather quickly without disrupting their home cage activities. Scientists can thus be encouraged to use mouse houses, also in view of the implementation of the EU Directive (2010/63/EU).     

Sex and boldness explain individual differences in spatial learning in a lizard

Understanding individual differences in cognitive performance is a major challenge to animal behaviour and cognition studies. We used the Eastern water skink (Eulamprus quoyii) to examine associations between exploration, boldness and individual variability in spatial learning, a dimension of lizard cognition with important bearing on fitness. We show that males perform better than females in a biologically relevant spatial learning task. This is the first evidence for sex differences in learning in a reptile, and we argue that it is probably owing to sex-specific selective pressures that may be widespread in lizards. Across the sexes, we found a clear association between boldness after a simulated predatory attack and the probability of learning the spatial task. In contrast to previous studies, we found a nonlinear association between boldness and learning: both ‘bold’ and ‘shy’ behavioural types were more successful learners than intermediate males. Our results do not fit with recent predictions suggesting that individual differences in learning may be linked with behavioural types via high–low-risk/reward trade-offs. We suggest the possibility that differences in spatial cognitive performance may arise in lizards as a consequence of the distinct environmental variability and complexity experienced by individuals as a result of their sex and social tactics.