Epigenetic responses to environmental factors, demonstrated by guinea pigs in the study of Weyrich et al. [ 80 ], could be their way of coping with climate change; it is feasible that further biological adaptations now exist to improve their tolerance of extreme weather. However, adaptation may never supersede the rate of climate change, so it is more likely that owners will need to adjust housing [ 81 ].
In Cameron et al. [ 52 ], wooden bases were common, but these should be avoided because urine, and therefore ammonia, accumulation can cause respiratory illness. Porous materials should be used only for easily changeable items like soft bedding, which also prevents pododermatitis [ 74 ], and was provided by most owners. Straw, which can be sharp and may cause eye injury, and mesh flooring, which can trap limbs, was used minimally, and more so outdoors [ 79 ].
It is recommended that enclosures be fully cleaned weekly, with daily spot cleans, as dirty and damp conditions can attract flies, which can cause myiasis [ 73 ]. In Cameron et al. [ 52 ], removal of droppings was generally infrequent but, overall, most owners employed regular cleaning of various aspects.
Hay was used as bedding in both Harrup and Rooney [ 49 ] and Cameron et al. [ 52 ]. Hay cannot be easily disinfected as it is absorbent and, instead, may need total replacement. More research is needed into its suitability compared with other materials. Dust can also cause respiratory diseases such as pneumonia [ 69 ], but it is unknown whether dust-free bedding was used. Respiratory disease and other infections can be treated with antibiotics, but guinea pigs are prone to dysbiosis and related complications so prophylaxis is preferable [ 18 ].
Only Cameron et al. [ 52 ] investigated enrichment, which is important for welfare as it prevents boredom [ 79 ]. Harrup and Rooney [ 49 ] could have explored this to address their research question more holistically. Owners mostly provided assortments of hides and toys made of safe, paper-based materials [ 82 ]. Worryingly, however, 11.2 %
of owners answered that hay was provided as a‘ toy’, which may demonstrate a demographic of owners who disregard hay as a dietary essential. It is further unknown whether the chews given were pesticide-free and made of non-poisonous woods [ 79 ].
Schumann et al. [ 53 ] focused on laboratory C. aperea and found a heightened sensitivity to change, particularly when transferred to smaller areas, and significantly lower blood cortisol in those housed outdoors than indoors. Although laboratory guinea pigs are not representative of pet guinea pigs, appropriate ethical protocols and housing are still crucial for the welfare of laboratory animals, which remain popular research subjects [ 35 ].
Negative situations may not always lead to cortisol changes, so unchanged values may not signify a lack of welfare-related issues [ 83 ]. The context is important, and whether harm or reward is more likely [ 83 ]. A range of behavioural indicators, such as ethograms, or physiological indicators may prove more fruitful, particularly as chronic issues often prompt compensatory mechanisms with other unpleasant consequences [ 84 ].
Companionship
Guinea pigs are highly sociable, so, to thrive and avoid adverse physiological changes from threat-avoidance behaviour [ 85 ], they must be housed with conspecifics( Figure 6). Harrup and Rooney [ 49 ] found this to be commonplace. Unsurprisingly, those housed with rabbits demonstrated frequent negative behaviours due to incompatible dietary requirements, lifestyles and temperaments [ 86 ]. Furthermore, rabbits can transmit pathogens that can cause fatal disease in guinea pigs, such as Bordetella bronchiseptica, of which rabbits are common asymptomatic carriers [ 87 ].
Although minimal, the exposure to inadequate diet, housing and husbandry aspects in such small, selfselected samples is worrisome as it may represent a more widespread problem.
Figure 6. Guinea pigs must be housed with conspecifics.
28 Veterinary Nursing Journal