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

Abstract

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 ¼ 12 cages) or unenriched cages (UC) (n ¼ 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.

Microbial lysate upregulates host oxytocin

“…By contrast, stimulation of social behavior or improving sense of well-being by enrichment of caging decreased corticosterone levels while counteracting thymus shrinkage in both mice and rats (Abou-Ismail and Mahboub, 2011; Seetharaman et al, 2016; Van Loo et al, 2004). A study in genetically engineered mice has provided direct evidence linking thymus gland size and function with corticosterone (Youn et al, 2011).…”

Small prey species’ behaviour and welfare: implications for veterinary professionals

“…Compromised welfare indicators are physical and behavioural (Poole 1997, Würbel 2001, Olsson et al . 2003, including behavioural inhibition, apathy, restlessness, changes in eating, grooming, repetitive and aggressive behaviours (Abou-Ismail & Mahboub 2011, Magnus & McBride 2017b ). Yet, the layperson may misinterpret such behaviours, inappropriately labelling them as "amusing", "wild" or "unhandleable" character traits or vices (McBride 2000 ), or as normal behaviour (Packer et al .…”

Environmentally Enriched Male Mink Gain More Copulations than Stereotypic, Barren-Reared Competitors

“…Deviations from symmetry (assessed as "fluctuating asymmetry", [46] cited in [47]) can be induced by stress during early ontogenic stages [48],[49], and symmetry is also potentially compromised by development in barren cages [50],[51]. Finally, immunocompetence and attributes that correlate with this are also important in mate choice [52], and yet impaired by both known stressors [53] and by impoverished housing [38],[54],[55]. Males raised in barren environments therefore seem at risk of developing into physically unattractive adults, but this idea has never been experimentally tested.…”

“…If such effects are mediated by HPA activation, then enrichment should reduce faecal glucocorticoid metabolites [85], and/or adrenal gland weight [55]) and have beneficial effects on traits relating to the HPG axis, with these effects correlating with reproductive benefits. If barren environments reduce male attractiveness, then enriched males should be heavier, more symmetrical, and/or show evidence of improved immunocompetence (e.g.…”